| /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of version 2 of the GNU General Public |
| * License as published by the Free Software Foundation. |
| * |
| * This program is distributed in the hope that it will be useful, but |
| * WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| * General Public License for more details. |
| */ |
| #include <linux/kernel.h> |
| #include <linux/types.h> |
| #include <linux/slab.h> |
| #include <linux/bpf.h> |
| #include <linux/filter.h> |
| #include <net/netlink.h> |
| #include <linux/file.h> |
| #include <linux/vmalloc.h> |
| |
| /* bpf_check() is a static code analyzer that walks eBPF program |
| * instruction by instruction and updates register/stack state. |
| * All paths of conditional branches are analyzed until 'bpf_exit' insn. |
| * |
| * The first pass is depth-first-search to check that the program is a DAG. |
| * It rejects the following programs: |
| * - larger than BPF_MAXINSNS insns |
| * - if loop is present (detected via back-edge) |
| * - unreachable insns exist (shouldn't be a forest. program = one function) |
| * - out of bounds or malformed jumps |
| * The second pass is all possible path descent from the 1st insn. |
| * Since it's analyzing all pathes through the program, the length of the |
| * analysis is limited to 32k insn, which may be hit even if total number of |
| * insn is less then 4K, but there are too many branches that change stack/regs. |
| * Number of 'branches to be analyzed' is limited to 1k |
| * |
| * On entry to each instruction, each register has a type, and the instruction |
| * changes the types of the registers depending on instruction semantics. |
| * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is |
| * copied to R1. |
| * |
| * All registers are 64-bit. |
| * R0 - return register |
| * R1-R5 argument passing registers |
| * R6-R9 callee saved registers |
| * R10 - frame pointer read-only |
| * |
| * At the start of BPF program the register R1 contains a pointer to bpf_context |
| * and has type PTR_TO_CTX. |
| * |
| * Verifier tracks arithmetic operations on pointers in case: |
| * BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), |
| * BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20), |
| * 1st insn copies R10 (which has FRAME_PTR) type into R1 |
| * and 2nd arithmetic instruction is pattern matched to recognize |
| * that it wants to construct a pointer to some element within stack. |
| * So after 2nd insn, the register R1 has type PTR_TO_STACK |
| * (and -20 constant is saved for further stack bounds checking). |
| * Meaning that this reg is a pointer to stack plus known immediate constant. |
| * |
| * Most of the time the registers have UNKNOWN_VALUE type, which |
| * means the register has some value, but it's not a valid pointer. |
| * (like pointer plus pointer becomes UNKNOWN_VALUE type) |
| * |
| * When verifier sees load or store instructions the type of base register |
| * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, FRAME_PTR. These are three pointer |
| * types recognized by check_mem_access() function. |
| * |
| * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value' |
| * and the range of [ptr, ptr + map's value_size) is accessible. |
| * |
| * registers used to pass values to function calls are checked against |
| * function argument constraints. |
| * |
| * ARG_PTR_TO_MAP_KEY is one of such argument constraints. |
| * It means that the register type passed to this function must be |
| * PTR_TO_STACK and it will be used inside the function as |
| * 'pointer to map element key' |
| * |
| * For example the argument constraints for bpf_map_lookup_elem(): |
| * .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, |
| * .arg1_type = ARG_CONST_MAP_PTR, |
| * .arg2_type = ARG_PTR_TO_MAP_KEY, |
| * |
| * ret_type says that this function returns 'pointer to map elem value or null' |
| * function expects 1st argument to be a const pointer to 'struct bpf_map' and |
| * 2nd argument should be a pointer to stack, which will be used inside |
| * the helper function as a pointer to map element key. |
| * |
| * On the kernel side the helper function looks like: |
| * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) |
| * { |
| * struct bpf_map *map = (struct bpf_map *) (unsigned long) r1; |
| * void *key = (void *) (unsigned long) r2; |
| * void *value; |
| * |
| * here kernel can access 'key' and 'map' pointers safely, knowing that |
| * [key, key + map->key_size) bytes are valid and were initialized on |
| * the stack of eBPF program. |
| * } |
| * |
| * Corresponding eBPF program may look like: |
| * BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR |
| * BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK |
| * BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP |
| * BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), |
| * here verifier looks at prototype of map_lookup_elem() and sees: |
| * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok, |
| * Now verifier knows that this map has key of R1->map_ptr->key_size bytes |
| * |
| * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far, |
| * Now verifier checks that [R2, R2 + map's key_size) are within stack limits |
| * and were initialized prior to this call. |
| * If it's ok, then verifier allows this BPF_CALL insn and looks at |
| * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets |
| * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function |
| * returns ether pointer to map value or NULL. |
| * |
| * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off' |
| * insn, the register holding that pointer in the true branch changes state to |
| * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false |
| * branch. See check_cond_jmp_op(). |
| * |
| * After the call R0 is set to return type of the function and registers R1-R5 |
| * are set to NOT_INIT to indicate that they are no longer readable. |
| */ |
| |
| /* types of values stored in eBPF registers */ |
| enum bpf_reg_type { |
| NOT_INIT = 0, /* nothing was written into register */ |
| UNKNOWN_VALUE, /* reg doesn't contain a valid pointer */ |
| PTR_TO_CTX, /* reg points to bpf_context */ |
| CONST_PTR_TO_MAP, /* reg points to struct bpf_map */ |
| PTR_TO_MAP_VALUE, /* reg points to map element value */ |
| PTR_TO_MAP_VALUE_OR_NULL,/* points to map elem value or NULL */ |
| FRAME_PTR, /* reg == frame_pointer */ |
| PTR_TO_STACK, /* reg == frame_pointer + imm */ |
| CONST_IMM, /* constant integer value */ |
| }; |
| |
| struct reg_state { |
| enum bpf_reg_type type; |
| union { |
| /* valid when type == CONST_IMM | PTR_TO_STACK */ |
| int imm; |
| |
| /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE | |
| * PTR_TO_MAP_VALUE_OR_NULL |
| */ |
| struct bpf_map *map_ptr; |
| }; |
| }; |
| |
| enum bpf_stack_slot_type { |
| STACK_INVALID, /* nothing was stored in this stack slot */ |
| STACK_SPILL, /* register spilled into stack */ |
| STACK_MISC /* BPF program wrote some data into this slot */ |
| }; |
| |
| #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */ |
| |
| /* state of the program: |
| * type of all registers and stack info |
| */ |
| struct verifier_state { |
| struct reg_state regs[MAX_BPF_REG]; |
| u8 stack_slot_type[MAX_BPF_STACK]; |
| struct reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE]; |
| }; |
| |
| /* linked list of verifier states used to prune search */ |
| struct verifier_state_list { |
| struct verifier_state state; |
| struct verifier_state_list *next; |
| }; |
| |
| /* verifier_state + insn_idx are pushed to stack when branch is encountered */ |
| struct verifier_stack_elem { |
| /* verifer state is 'st' |
| * before processing instruction 'insn_idx' |
| * and after processing instruction 'prev_insn_idx' |
| */ |
| struct verifier_state st; |
| int insn_idx; |
| int prev_insn_idx; |
| struct verifier_stack_elem *next; |
| }; |
| |
| #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */ |
| |
| /* single container for all structs |
| * one verifier_env per bpf_check() call |
| */ |
| struct verifier_env { |
| struct bpf_prog *prog; /* eBPF program being verified */ |
| struct verifier_stack_elem *head; /* stack of verifier states to be processed */ |
| int stack_size; /* number of states to be processed */ |
| struct verifier_state cur_state; /* current verifier state */ |
| struct verifier_state_list **explored_states; /* search pruning optimization */ |
| struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */ |
| u32 used_map_cnt; /* number of used maps */ |
| bool allow_ptr_leaks; |
| }; |
| |
| #define BPF_COMPLEXITY_LIMIT_INSNS 65536 |
| #define BPF_COMPLEXITY_LIMIT_STACK 1024 |
| |
| /* verbose verifier prints what it's seeing |
| * bpf_check() is called under lock, so no race to access these global vars |
| */ |
| static u32 log_level, log_size, log_len; |
| static char *log_buf; |
| |
| static DEFINE_MUTEX(bpf_verifier_lock); |
| |
| /* log_level controls verbosity level of eBPF verifier. |
| * verbose() is used to dump the verification trace to the log, so the user |
| * can figure out what's wrong with the program |
| */ |
| static __printf(1, 2) void verbose(const char *fmt, ...) |
| { |
| va_list args; |
| |
| if (log_level == 0 || log_len >= log_size - 1) |
| return; |
| |
| va_start(args, fmt); |
| log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args); |
| va_end(args); |
| } |
| |
| /* string representation of 'enum bpf_reg_type' */ |
| static const char * const reg_type_str[] = { |
| [NOT_INIT] = "?", |
| [UNKNOWN_VALUE] = "inv", |
| [PTR_TO_CTX] = "ctx", |
| [CONST_PTR_TO_MAP] = "map_ptr", |
| [PTR_TO_MAP_VALUE] = "map_value", |
| [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null", |
| [FRAME_PTR] = "fp", |
| [PTR_TO_STACK] = "fp", |
| [CONST_IMM] = "imm", |
| }; |
| |
| static const struct { |
| int map_type; |
| int func_id; |
| } func_limit[] = { |
| {BPF_MAP_TYPE_PROG_ARRAY, BPF_FUNC_tail_call}, |
| {BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_read}, |
| {BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_output}, |
| {BPF_MAP_TYPE_STACK_TRACE, BPF_FUNC_get_stackid}, |
| }; |
| |
| static void print_verifier_state(struct verifier_env *env) |
| { |
| enum bpf_reg_type t; |
| int i; |
| |
| for (i = 0; i < MAX_BPF_REG; i++) { |
| t = env->cur_state.regs[i].type; |
| if (t == NOT_INIT) |
| continue; |
| verbose(" R%d=%s", i, reg_type_str[t]); |
| if (t == CONST_IMM || t == PTR_TO_STACK) |
| verbose("%d", env->cur_state.regs[i].imm); |
| else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE || |
| t == PTR_TO_MAP_VALUE_OR_NULL) |
| verbose("(ks=%d,vs=%d)", |
| env->cur_state.regs[i].map_ptr->key_size, |
| env->cur_state.regs[i].map_ptr->value_size); |
| } |
| for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { |
| if (env->cur_state.stack_slot_type[i] == STACK_SPILL) |
| verbose(" fp%d=%s", -MAX_BPF_STACK + i, |
| reg_type_str[env->cur_state.spilled_regs[i / BPF_REG_SIZE].type]); |
| } |
| verbose("\n"); |
| } |
| |
| static const char *const bpf_class_string[] = { |
| [BPF_LD] = "ld", |
| [BPF_LDX] = "ldx", |
| [BPF_ST] = "st", |
| [BPF_STX] = "stx", |
| [BPF_ALU] = "alu", |
| [BPF_JMP] = "jmp", |
| [BPF_RET] = "BUG", |
| [BPF_ALU64] = "alu64", |
| }; |
| |
| static const char *const bpf_alu_string[16] = { |
| [BPF_ADD >> 4] = "+=", |
| [BPF_SUB >> 4] = "-=", |
| [BPF_MUL >> 4] = "*=", |
| [BPF_DIV >> 4] = "/=", |
| [BPF_OR >> 4] = "|=", |
| [BPF_AND >> 4] = "&=", |
| [BPF_LSH >> 4] = "<<=", |
| [BPF_RSH >> 4] = ">>=", |
| [BPF_NEG >> 4] = "neg", |
| [BPF_MOD >> 4] = "%=", |
| [BPF_XOR >> 4] = "^=", |
| [BPF_MOV >> 4] = "=", |
| [BPF_ARSH >> 4] = "s>>=", |
| [BPF_END >> 4] = "endian", |
| }; |
| |
| static const char *const bpf_ldst_string[] = { |
| [BPF_W >> 3] = "u32", |
| [BPF_H >> 3] = "u16", |
| [BPF_B >> 3] = "u8", |
| [BPF_DW >> 3] = "u64", |
| }; |
| |
| static const char *const bpf_jmp_string[16] = { |
| [BPF_JA >> 4] = "jmp", |
| [BPF_JEQ >> 4] = "==", |
| [BPF_JGT >> 4] = ">", |
| [BPF_JGE >> 4] = ">=", |
| [BPF_JSET >> 4] = "&", |
| [BPF_JNE >> 4] = "!=", |
| [BPF_JSGT >> 4] = "s>", |
| [BPF_JSGE >> 4] = "s>=", |
| [BPF_CALL >> 4] = "call", |
| [BPF_EXIT >> 4] = "exit", |
| }; |
| |
| static void print_bpf_insn(struct bpf_insn *insn) |
| { |
| u8 class = BPF_CLASS(insn->code); |
| |
| if (class == BPF_ALU || class == BPF_ALU64) { |
| if (BPF_SRC(insn->code) == BPF_X) |
| verbose("(%02x) %sr%d %s %sr%d\n", |
| insn->code, class == BPF_ALU ? "(u32) " : "", |
| insn->dst_reg, |
| bpf_alu_string[BPF_OP(insn->code) >> 4], |
| class == BPF_ALU ? "(u32) " : "", |
| insn->src_reg); |
| else |
| verbose("(%02x) %sr%d %s %s%d\n", |
| insn->code, class == BPF_ALU ? "(u32) " : "", |
| insn->dst_reg, |
| bpf_alu_string[BPF_OP(insn->code) >> 4], |
| class == BPF_ALU ? "(u32) " : "", |
| insn->imm); |
| } else if (class == BPF_STX) { |
| if (BPF_MODE(insn->code) == BPF_MEM) |
| verbose("(%02x) *(%s *)(r%d %+d) = r%d\n", |
| insn->code, |
| bpf_ldst_string[BPF_SIZE(insn->code) >> 3], |
| insn->dst_reg, |
| insn->off, insn->src_reg); |
| else if (BPF_MODE(insn->code) == BPF_XADD) |
| verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n", |
| insn->code, |
| bpf_ldst_string[BPF_SIZE(insn->code) >> 3], |
| insn->dst_reg, insn->off, |
| insn->src_reg); |
| else |
| verbose("BUG_%02x\n", insn->code); |
| } else if (class == BPF_ST) { |
| if (BPF_MODE(insn->code) != BPF_MEM) { |
| verbose("BUG_st_%02x\n", insn->code); |
| return; |
| } |
| verbose("(%02x) *(%s *)(r%d %+d) = %d\n", |
| insn->code, |
| bpf_ldst_string[BPF_SIZE(insn->code) >> 3], |
| insn->dst_reg, |
| insn->off, insn->imm); |
| } else if (class == BPF_LDX) { |
| if (BPF_MODE(insn->code) != BPF_MEM) { |
| verbose("BUG_ldx_%02x\n", insn->code); |
| return; |
| } |
| verbose("(%02x) r%d = *(%s *)(r%d %+d)\n", |
| insn->code, insn->dst_reg, |
| bpf_ldst_string[BPF_SIZE(insn->code) >> 3], |
| insn->src_reg, insn->off); |
| } else if (class == BPF_LD) { |
| if (BPF_MODE(insn->code) == BPF_ABS) { |
| verbose("(%02x) r0 = *(%s *)skb[%d]\n", |
| insn->code, |
| bpf_ldst_string[BPF_SIZE(insn->code) >> 3], |
| insn->imm); |
| } else if (BPF_MODE(insn->code) == BPF_IND) { |
| verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n", |
| insn->code, |
| bpf_ldst_string[BPF_SIZE(insn->code) >> 3], |
| insn->src_reg, insn->imm); |
| } else if (BPF_MODE(insn->code) == BPF_IMM) { |
| verbose("(%02x) r%d = 0x%x\n", |
| insn->code, insn->dst_reg, insn->imm); |
| } else { |
| verbose("BUG_ld_%02x\n", insn->code); |
| return; |
| } |
| } else if (class == BPF_JMP) { |
| u8 opcode = BPF_OP(insn->code); |
| |
| if (opcode == BPF_CALL) { |
| verbose("(%02x) call %d\n", insn->code, insn->imm); |
| } else if (insn->code == (BPF_JMP | BPF_JA)) { |
| verbose("(%02x) goto pc%+d\n", |
| insn->code, insn->off); |
| } else if (insn->code == (BPF_JMP | BPF_EXIT)) { |
| verbose("(%02x) exit\n", insn->code); |
| } else if (BPF_SRC(insn->code) == BPF_X) { |
| verbose("(%02x) if r%d %s r%d goto pc%+d\n", |
| insn->code, insn->dst_reg, |
| bpf_jmp_string[BPF_OP(insn->code) >> 4], |
| insn->src_reg, insn->off); |
| } else { |
| verbose("(%02x) if r%d %s 0x%x goto pc%+d\n", |
| insn->code, insn->dst_reg, |
| bpf_jmp_string[BPF_OP(insn->code) >> 4], |
| insn->imm, insn->off); |
| } |
| } else { |
| verbose("(%02x) %s\n", insn->code, bpf_class_string[class]); |
| } |
| } |
| |
| static int pop_stack(struct verifier_env *env, int *prev_insn_idx) |
| { |
| struct verifier_stack_elem *elem; |
| int insn_idx; |
| |
| if (env->head == NULL) |
| return -1; |
| |
| memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state)); |
| insn_idx = env->head->insn_idx; |
| if (prev_insn_idx) |
| *prev_insn_idx = env->head->prev_insn_idx; |
| elem = env->head->next; |
| kfree(env->head); |
| env->head = elem; |
| env->stack_size--; |
| return insn_idx; |
| } |
| |
| static struct verifier_state *push_stack(struct verifier_env *env, int insn_idx, |
| int prev_insn_idx) |
| { |
| struct verifier_stack_elem *elem; |
| |
| elem = kmalloc(sizeof(struct verifier_stack_elem), GFP_KERNEL); |
| if (!elem) |
| goto err; |
| |
| memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state)); |
| elem->insn_idx = insn_idx; |
| elem->prev_insn_idx = prev_insn_idx; |
| elem->next = env->head; |
| env->head = elem; |
| env->stack_size++; |
| if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) { |
| verbose("BPF program is too complex\n"); |
| goto err; |
| } |
| return &elem->st; |
| err: |
| /* pop all elements and return */ |
| while (pop_stack(env, NULL) >= 0); |
| return NULL; |
| } |
| |
| #define CALLER_SAVED_REGS 6 |
| static const int caller_saved[CALLER_SAVED_REGS] = { |
| BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5 |
| }; |
| |
| static void init_reg_state(struct reg_state *regs) |
| { |
| int i; |
| |
| for (i = 0; i < MAX_BPF_REG; i++) { |
| regs[i].type = NOT_INIT; |
| regs[i].imm = 0; |
| regs[i].map_ptr = NULL; |
| } |
| |
| /* frame pointer */ |
| regs[BPF_REG_FP].type = FRAME_PTR; |
| |
| /* 1st arg to a function */ |
| regs[BPF_REG_1].type = PTR_TO_CTX; |
| } |
| |
| static void mark_reg_unknown_value(struct reg_state *regs, u32 regno) |
| { |
| BUG_ON(regno >= MAX_BPF_REG); |
| regs[regno].type = UNKNOWN_VALUE; |
| regs[regno].imm = 0; |
| regs[regno].map_ptr = NULL; |
| } |
| |
| enum reg_arg_type { |
| SRC_OP, /* register is used as source operand */ |
| DST_OP, /* register is used as destination operand */ |
| DST_OP_NO_MARK /* same as above, check only, don't mark */ |
| }; |
| |
| static int check_reg_arg(struct reg_state *regs, u32 regno, |
| enum reg_arg_type t) |
| { |
| if (regno >= MAX_BPF_REG) { |
| verbose("R%d is invalid\n", regno); |
| return -EINVAL; |
| } |
| |
| if (t == SRC_OP) { |
| /* check whether register used as source operand can be read */ |
| if (regs[regno].type == NOT_INIT) { |
| verbose("R%d !read_ok\n", regno); |
| return -EACCES; |
| } |
| } else { |
| /* check whether register used as dest operand can be written to */ |
| if (regno == BPF_REG_FP) { |
| verbose("frame pointer is read only\n"); |
| return -EACCES; |
| } |
| if (t == DST_OP) |
| mark_reg_unknown_value(regs, regno); |
| } |
| return 0; |
| } |
| |
| static int bpf_size_to_bytes(int bpf_size) |
| { |
| if (bpf_size == BPF_W) |
| return 4; |
| else if (bpf_size == BPF_H) |
| return 2; |
| else if (bpf_size == BPF_B) |
| return 1; |
| else if (bpf_size == BPF_DW) |
| return 8; |
| else |
| return -EINVAL; |
| } |
| |
| static bool is_spillable_regtype(enum bpf_reg_type type) |
| { |
| switch (type) { |
| case PTR_TO_MAP_VALUE: |
| case PTR_TO_MAP_VALUE_OR_NULL: |
| case PTR_TO_STACK: |
| case PTR_TO_CTX: |
| case FRAME_PTR: |
| case CONST_PTR_TO_MAP: |
| return true; |
| default: |
| return false; |
| } |
| } |
| |
| /* check_stack_read/write functions track spill/fill of registers, |
| * stack boundary and alignment are checked in check_mem_access() |
| */ |
| static int check_stack_write(struct verifier_state *state, int off, int size, |
| int value_regno) |
| { |
| int i; |
| /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0, |
| * so it's aligned access and [off, off + size) are within stack limits |
| */ |
| |
| if (value_regno >= 0 && |
| is_spillable_regtype(state->regs[value_regno].type)) { |
| |
| /* register containing pointer is being spilled into stack */ |
| if (size != BPF_REG_SIZE) { |
| verbose("invalid size of register spill\n"); |
| return -EACCES; |
| } |
| |
| /* save register state */ |
| state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = |
| state->regs[value_regno]; |
| |
| for (i = 0; i < BPF_REG_SIZE; i++) |
| state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL; |
| } else { |
| /* regular write of data into stack */ |
| state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = |
| (struct reg_state) {}; |
| |
| for (i = 0; i < size; i++) |
| state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC; |
| } |
| return 0; |
| } |
| |
| static int check_stack_read(struct verifier_state *state, int off, int size, |
| int value_regno) |
| { |
| u8 *slot_type; |
| int i; |
| |
| slot_type = &state->stack_slot_type[MAX_BPF_STACK + off]; |
| |
| if (slot_type[0] == STACK_SPILL) { |
| if (size != BPF_REG_SIZE) { |
| verbose("invalid size of register spill\n"); |
| return -EACCES; |
| } |
| for (i = 1; i < BPF_REG_SIZE; i++) { |
| if (slot_type[i] != STACK_SPILL) { |
| verbose("corrupted spill memory\n"); |
| return -EACCES; |
| } |
| } |
| |
| if (value_regno >= 0) |
| /* restore register state from stack */ |
| state->regs[value_regno] = |
| state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE]; |
| return 0; |
| } else { |
| for (i = 0; i < size; i++) { |
| if (slot_type[i] != STACK_MISC) { |
| verbose("invalid read from stack off %d+%d size %d\n", |
| off, i, size); |
| return -EACCES; |
| } |
| } |
| if (value_regno >= 0) |
| /* have read misc data from the stack */ |
| mark_reg_unknown_value(state->regs, value_regno); |
| return 0; |
| } |
| } |
| |
| /* check read/write into map element returned by bpf_map_lookup_elem() */ |
| static int check_map_access(struct verifier_env *env, u32 regno, int off, |
| int size) |
| { |
| struct bpf_map *map = env->cur_state.regs[regno].map_ptr; |
| |
| if (off < 0 || off + size > map->value_size) { |
| verbose("invalid access to map value, value_size=%d off=%d size=%d\n", |
| map->value_size, off, size); |
| return -EACCES; |
| } |
| return 0; |
| } |
| |
| /* check access to 'struct bpf_context' fields */ |
| static int check_ctx_access(struct verifier_env *env, int off, int size, |
| enum bpf_access_type t) |
| { |
| if (env->prog->aux->ops->is_valid_access && |
| env->prog->aux->ops->is_valid_access(off, size, t)) { |
| /* remember the offset of last byte accessed in ctx */ |
| if (env->prog->aux->max_ctx_offset < off + size) |
| env->prog->aux->max_ctx_offset = off + size; |
| return 0; |
| } |
| |
| verbose("invalid bpf_context access off=%d size=%d\n", off, size); |
| return -EACCES; |
| } |
| |
| static bool is_pointer_value(struct verifier_env *env, int regno) |
| { |
| if (env->allow_ptr_leaks) |
| return false; |
| |
| switch (env->cur_state.regs[regno].type) { |
| case UNKNOWN_VALUE: |
| case CONST_IMM: |
| return false; |
| default: |
| return true; |
| } |
| } |
| |
| /* check whether memory at (regno + off) is accessible for t = (read | write) |
| * if t==write, value_regno is a register which value is stored into memory |
| * if t==read, value_regno is a register which will receive the value from memory |
| * if t==write && value_regno==-1, some unknown value is stored into memory |
| * if t==read && value_regno==-1, don't care what we read from memory |
| */ |
| static int check_mem_access(struct verifier_env *env, u32 regno, int off, |
| int bpf_size, enum bpf_access_type t, |
| int value_regno) |
| { |
| struct verifier_state *state = &env->cur_state; |
| int size, err = 0; |
| |
| if (state->regs[regno].type == PTR_TO_STACK) |
| off += state->regs[regno].imm; |
| |
| size = bpf_size_to_bytes(bpf_size); |
| if (size < 0) |
| return size; |
| |
| if (off % size != 0) { |
| verbose("misaligned access off %d size %d\n", off, size); |
| return -EACCES; |
| } |
| |
| if (state->regs[regno].type == PTR_TO_MAP_VALUE) { |
| if (t == BPF_WRITE && value_regno >= 0 && |
| is_pointer_value(env, value_regno)) { |
| verbose("R%d leaks addr into map\n", value_regno); |
| return -EACCES; |
| } |
| err = check_map_access(env, regno, off, size); |
| if (!err && t == BPF_READ && value_regno >= 0) |
| mark_reg_unknown_value(state->regs, value_regno); |
| |
| } else if (state->regs[regno].type == PTR_TO_CTX) { |
| if (t == BPF_WRITE && value_regno >= 0 && |
| is_pointer_value(env, value_regno)) { |
| verbose("R%d leaks addr into ctx\n", value_regno); |
| return -EACCES; |
| } |
| err = check_ctx_access(env, off, size, t); |
| if (!err && t == BPF_READ && value_regno >= 0) |
| mark_reg_unknown_value(state->regs, value_regno); |
| |
| } else if (state->regs[regno].type == FRAME_PTR || |
| state->regs[regno].type == PTR_TO_STACK) { |
| if (off >= 0 || off < -MAX_BPF_STACK) { |
| verbose("invalid stack off=%d size=%d\n", off, size); |
| return -EACCES; |
| } |
| if (t == BPF_WRITE) { |
| if (!env->allow_ptr_leaks && |
| state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL && |
| size != BPF_REG_SIZE) { |
| verbose("attempt to corrupt spilled pointer on stack\n"); |
| return -EACCES; |
| } |
| err = check_stack_write(state, off, size, value_regno); |
| } else { |
| err = check_stack_read(state, off, size, value_regno); |
| } |
| } else { |
| verbose("R%d invalid mem access '%s'\n", |
| regno, reg_type_str[state->regs[regno].type]); |
| return -EACCES; |
| } |
| return err; |
| } |
| |
| static int check_xadd(struct verifier_env *env, struct bpf_insn *insn) |
| { |
| struct reg_state *regs = env->cur_state.regs; |
| int err; |
| |
| if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) || |
| insn->imm != 0) { |
| verbose("BPF_XADD uses reserved fields\n"); |
| return -EINVAL; |
| } |
| |
| /* check src1 operand */ |
| err = check_reg_arg(regs, insn->src_reg, SRC_OP); |
| if (err) |
| return err; |
| |
| /* check src2 operand */ |
| err = check_reg_arg(regs, insn->dst_reg, SRC_OP); |
| if (err) |
| return err; |
| |
| /* check whether atomic_add can read the memory */ |
| err = check_mem_access(env, insn->dst_reg, insn->off, |
| BPF_SIZE(insn->code), BPF_READ, -1); |
| if (err) |
| return err; |
| |
| /* check whether atomic_add can write into the same memory */ |
| return check_mem_access(env, insn->dst_reg, insn->off, |
| BPF_SIZE(insn->code), BPF_WRITE, -1); |
| } |
| |
| /* when register 'regno' is passed into function that will read 'access_size' |
| * bytes from that pointer, make sure that it's within stack boundary |
| * and all elements of stack are initialized |
| */ |
| static int check_stack_boundary(struct verifier_env *env, int regno, |
| int access_size, bool zero_size_allowed) |
| { |
| struct verifier_state *state = &env->cur_state; |
| struct reg_state *regs = state->regs; |
| int off, i; |
| |
| if (regs[regno].type != PTR_TO_STACK) { |
| if (zero_size_allowed && access_size == 0 && |
| regs[regno].type == CONST_IMM && |
| regs[regno].imm == 0) |
| return 0; |
| |
| verbose("R%d type=%s expected=%s\n", regno, |
| reg_type_str[regs[regno].type], |
| reg_type_str[PTR_TO_STACK]); |
| return -EACCES; |
| } |
| |
| off = regs[regno].imm; |
| if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 || |
| access_size <= 0) { |
| verbose("invalid stack type R%d off=%d access_size=%d\n", |
| regno, off, access_size); |
| return -EACCES; |
| } |
| |
| for (i = 0; i < access_size; i++) { |
| if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) { |
| verbose("invalid indirect read from stack off %d+%d size %d\n", |
| off, i, access_size); |
| return -EACCES; |
| } |
| } |
| return 0; |
| } |
| |
| static int check_func_arg(struct verifier_env *env, u32 regno, |
| enum bpf_arg_type arg_type, struct bpf_map **mapp) |
| { |
| struct reg_state *reg = env->cur_state.regs + regno; |
| enum bpf_reg_type expected_type; |
| int err = 0; |
| |
| if (arg_type == ARG_DONTCARE) |
| return 0; |
| |
| if (reg->type == NOT_INIT) { |
| verbose("R%d !read_ok\n", regno); |
| return -EACCES; |
| } |
| |
| if (arg_type == ARG_ANYTHING) { |
| if (is_pointer_value(env, regno)) { |
| verbose("R%d leaks addr into helper function\n", regno); |
| return -EACCES; |
| } |
| return 0; |
| } |
| |
| if (arg_type == ARG_PTR_TO_MAP_KEY || |
| arg_type == ARG_PTR_TO_MAP_VALUE) { |
| expected_type = PTR_TO_STACK; |
| } else if (arg_type == ARG_CONST_STACK_SIZE || |
| arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) { |
| expected_type = CONST_IMM; |
| } else if (arg_type == ARG_CONST_MAP_PTR) { |
| expected_type = CONST_PTR_TO_MAP; |
| } else if (arg_type == ARG_PTR_TO_CTX) { |
| expected_type = PTR_TO_CTX; |
| } else if (arg_type == ARG_PTR_TO_STACK) { |
| expected_type = PTR_TO_STACK; |
| /* One exception here. In case function allows for NULL to be |
| * passed in as argument, it's a CONST_IMM type. Final test |
| * happens during stack boundary checking. |
| */ |
| if (reg->type == CONST_IMM && reg->imm == 0) |
| expected_type = CONST_IMM; |
| } else { |
| verbose("unsupported arg_type %d\n", arg_type); |
| return -EFAULT; |
| } |
| |
| if (reg->type != expected_type) { |
| verbose("R%d type=%s expected=%s\n", regno, |
| reg_type_str[reg->type], reg_type_str[expected_type]); |
| return -EACCES; |
| } |
| |
| if (arg_type == ARG_CONST_MAP_PTR) { |
| /* bpf_map_xxx(map_ptr) call: remember that map_ptr */ |
| *mapp = reg->map_ptr; |
| |
| } else if (arg_type == ARG_PTR_TO_MAP_KEY) { |
| /* bpf_map_xxx(..., map_ptr, ..., key) call: |
| * check that [key, key + map->key_size) are within |
| * stack limits and initialized |
| */ |
| if (!*mapp) { |
| /* in function declaration map_ptr must come before |
| * map_key, so that it's verified and known before |
| * we have to check map_key here. Otherwise it means |
| * that kernel subsystem misconfigured verifier |
| */ |
| verbose("invalid map_ptr to access map->key\n"); |
| return -EACCES; |
| } |
| err = check_stack_boundary(env, regno, (*mapp)->key_size, |
| false); |
| } else if (arg_type == ARG_PTR_TO_MAP_VALUE) { |
| /* bpf_map_xxx(..., map_ptr, ..., value) call: |
| * check [value, value + map->value_size) validity |
| */ |
| if (!*mapp) { |
| /* kernel subsystem misconfigured verifier */ |
| verbose("invalid map_ptr to access map->value\n"); |
| return -EACCES; |
| } |
| err = check_stack_boundary(env, regno, (*mapp)->value_size, |
| false); |
| } else if (arg_type == ARG_CONST_STACK_SIZE || |
| arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) { |
| bool zero_size_allowed = (arg_type == ARG_CONST_STACK_SIZE_OR_ZERO); |
| |
| /* bpf_xxx(..., buf, len) call will access 'len' bytes |
| * from stack pointer 'buf'. Check it |
| * note: regno == len, regno - 1 == buf |
| */ |
| if (regno == 0) { |
| /* kernel subsystem misconfigured verifier */ |
| verbose("ARG_CONST_STACK_SIZE cannot be first argument\n"); |
| return -EACCES; |
| } |
| err = check_stack_boundary(env, regno - 1, reg->imm, |
| zero_size_allowed); |
| } |
| |
| return err; |
| } |
| |
| static int check_map_func_compatibility(struct bpf_map *map, int func_id) |
| { |
| bool bool_map, bool_func; |
| int i; |
| |
| if (!map) |
| return 0; |
| |
| for (i = 0; i < ARRAY_SIZE(func_limit); i++) { |
| bool_map = (map->map_type == func_limit[i].map_type); |
| bool_func = (func_id == func_limit[i].func_id); |
| /* only when map & func pair match it can continue. |
| * don't allow any other map type to be passed into |
| * the special func; |
| */ |
| if (bool_func && bool_map != bool_func) { |
| verbose("cannot pass map_type %d into func %d\n", |
| map->map_type, func_id); |
| return -EINVAL; |
| } |
| } |
| |
| return 0; |
| } |
| |
| static int check_call(struct verifier_env *env, int func_id) |
| { |
| struct verifier_state *state = &env->cur_state; |
| const struct bpf_func_proto *fn = NULL; |
| struct reg_state *regs = state->regs; |
| struct bpf_map *map = NULL; |
| struct reg_state *reg; |
| int i, err; |
| |
| /* find function prototype */ |
| if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) { |
| verbose("invalid func %d\n", func_id); |
| return -EINVAL; |
| } |
| |
| if (env->prog->aux->ops->get_func_proto) |
| fn = env->prog->aux->ops->get_func_proto(func_id); |
| |
| if (!fn) { |
| verbose("unknown func %d\n", func_id); |
| return -EINVAL; |
| } |
| |
| /* eBPF programs must be GPL compatible to use GPL-ed functions */ |
| if (!env->prog->gpl_compatible && fn->gpl_only) { |
| verbose("cannot call GPL only function from proprietary program\n"); |
| return -EINVAL; |
| } |
| |
| /* check args */ |
| err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &map); |
| if (err) |
| return err; |
| err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &map); |
| if (err) |
| return err; |
| err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &map); |
| if (err) |
| return err; |
| err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &map); |
| if (err) |
| return err; |
| err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &map); |
| if (err) |
| return err; |
| |
| /* reset caller saved regs */ |
| for (i = 0; i < CALLER_SAVED_REGS; i++) { |
| reg = regs + caller_saved[i]; |
| reg->type = NOT_INIT; |
| reg->imm = 0; |
| } |
| |
| /* update return register */ |
| if (fn->ret_type == RET_INTEGER) { |
| regs[BPF_REG_0].type = UNKNOWN_VALUE; |
| } else if (fn->ret_type == RET_VOID) { |
| regs[BPF_REG_0].type = NOT_INIT; |
| } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) { |
| regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL; |
| /* remember map_ptr, so that check_map_access() |
| * can check 'value_size' boundary of memory access |
| * to map element returned from bpf_map_lookup_elem() |
| */ |
| if (map == NULL) { |
| verbose("kernel subsystem misconfigured verifier\n"); |
| return -EINVAL; |
| } |
| regs[BPF_REG_0].map_ptr = map; |
| } else { |
| verbose("unknown return type %d of func %d\n", |
| fn->ret_type, func_id); |
| return -EINVAL; |
| } |
| |
| err = check_map_func_compatibility(map, func_id); |
| if (err) |
| return err; |
| |
| return 0; |
| } |
| |
| /* check validity of 32-bit and 64-bit arithmetic operations */ |
| static int check_alu_op(struct verifier_env *env, struct bpf_insn *insn) |
| { |
| struct reg_state *regs = env->cur_state.regs; |
| u8 opcode = BPF_OP(insn->code); |
| int err; |
| |
| if (opcode == BPF_END || opcode == BPF_NEG) { |
| if (opcode == BPF_NEG) { |
| if (BPF_SRC(insn->code) != 0 || |
| insn->src_reg != BPF_REG_0 || |
| insn->off != 0 || insn->imm != 0) { |
| verbose("BPF_NEG uses reserved fields\n"); |
| return -EINVAL; |
| } |
| } else { |
| if (insn->src_reg != BPF_REG_0 || insn->off != 0 || |
| (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) { |
| verbose("BPF_END uses reserved fields\n"); |
| return -EINVAL; |
| } |
| } |
| |
| /* check src operand */ |
| err = check_reg_arg(regs, insn->dst_reg, SRC_OP); |
| if (err) |
| return err; |
| |
| if (is_pointer_value(env, insn->dst_reg)) { |
| verbose("R%d pointer arithmetic prohibited\n", |
| insn->dst_reg); |
| return -EACCES; |
| } |
| |
| /* check dest operand */ |
| err = check_reg_arg(regs, insn->dst_reg, DST_OP); |
| if (err) |
| return err; |
| |
| } else if (opcode == BPF_MOV) { |
| |
| if (BPF_SRC(insn->code) == BPF_X) { |
| if (insn->imm != 0 || insn->off != 0) { |
| verbose("BPF_MOV uses reserved fields\n"); |
| return -EINVAL; |
| } |
| |
| /* check src operand */ |
| err = check_reg_arg(regs, insn->src_reg, SRC_OP); |
| if (err) |
| return err; |
| } else { |
| if (insn->src_reg != BPF_REG_0 || insn->off != 0) { |
| verbose("BPF_MOV uses reserved fields\n"); |
| return -EINVAL; |
| } |
| } |
| |
| /* check dest operand */ |
| err = check_reg_arg(regs, insn->dst_reg, DST_OP); |
| if (err) |
| return err; |
| |
| if (BPF_SRC(insn->code) == BPF_X) { |
| if (BPF_CLASS(insn->code) == BPF_ALU64) { |
| /* case: R1 = R2 |
| * copy register state to dest reg |
| */ |
| regs[insn->dst_reg] = regs[insn->src_reg]; |
| } else { |
| if (is_pointer_value(env, insn->src_reg)) { |
| verbose("R%d partial copy of pointer\n", |
| insn->src_reg); |
| return -EACCES; |
| } |
| regs[insn->dst_reg].type = UNKNOWN_VALUE; |
| regs[insn->dst_reg].map_ptr = NULL; |
| } |
| } else { |
| /* case: R = imm |
| * remember the value we stored into this reg |
| */ |
| regs[insn->dst_reg].type = CONST_IMM; |
| regs[insn->dst_reg].imm = insn->imm; |
| } |
| |
| } else if (opcode > BPF_END) { |
| verbose("invalid BPF_ALU opcode %x\n", opcode); |
| return -EINVAL; |
| |
| } else { /* all other ALU ops: and, sub, xor, add, ... */ |
| |
| bool stack_relative = false; |
| |
| if (BPF_SRC(insn->code) == BPF_X) { |
| if (insn->imm != 0 || insn->off != 0) { |
| verbose("BPF_ALU uses reserved fields\n"); |
| return -EINVAL; |
| } |
| /* check src1 operand */ |
| err = check_reg_arg(regs, insn->src_reg, SRC_OP); |
| if (err) |
| return err; |
| } else { |
| if (insn->src_reg != BPF_REG_0 || insn->off != 0) { |
| verbose("BPF_ALU uses reserved fields\n"); |
| return -EINVAL; |
| } |
| } |
| |
| /* check src2 operand */ |
| err = check_reg_arg(regs, insn->dst_reg, SRC_OP); |
| if (err) |
| return err; |
| |
| if ((opcode == BPF_MOD || opcode == BPF_DIV) && |
| BPF_SRC(insn->code) == BPF_K && insn->imm == 0) { |
| verbose("div by zero\n"); |
| return -EINVAL; |
| } |
| |
| if ((opcode == BPF_LSH || opcode == BPF_RSH || |
| opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) { |
| int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32; |
| |
| if (insn->imm < 0 || insn->imm >= size) { |
| verbose("invalid shift %d\n", insn->imm); |
| return -EINVAL; |
| } |
| } |
| |
| /* pattern match 'bpf_add Rx, imm' instruction */ |
| if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 && |
| regs[insn->dst_reg].type == FRAME_PTR && |
| BPF_SRC(insn->code) == BPF_K) { |
| stack_relative = true; |
| } else if (is_pointer_value(env, insn->dst_reg)) { |
| verbose("R%d pointer arithmetic prohibited\n", |
| insn->dst_reg); |
| return -EACCES; |
| } else if (BPF_SRC(insn->code) == BPF_X && |
| is_pointer_value(env, insn->src_reg)) { |
| verbose("R%d pointer arithmetic prohibited\n", |
| insn->src_reg); |
| return -EACCES; |
| } |
| |
| /* check dest operand */ |
| err = check_reg_arg(regs, insn->dst_reg, DST_OP); |
| if (err) |
| return err; |
| |
| if (stack_relative) { |
| regs[insn->dst_reg].type = PTR_TO_STACK; |
| regs[insn->dst_reg].imm = insn->imm; |
| } |
| } |
| |
| return 0; |
| } |
| |
| static int check_cond_jmp_op(struct verifier_env *env, |
| struct bpf_insn *insn, int *insn_idx) |
| { |
| struct reg_state *regs = env->cur_state.regs; |
| struct verifier_state *other_branch; |
| u8 opcode = BPF_OP(insn->code); |
| int err; |
| |
| if (opcode > BPF_EXIT) { |
| verbose("invalid BPF_JMP opcode %x\n", opcode); |
| return -EINVAL; |
| } |
| |
| if (BPF_SRC(insn->code) == BPF_X) { |
| if (insn->imm != 0) { |
| verbose("BPF_JMP uses reserved fields\n"); |
| return -EINVAL; |
| } |
| |
| /* check src1 operand */ |
| err = check_reg_arg(regs, insn->src_reg, SRC_OP); |
| if (err) |
| return err; |
| |
| if (is_pointer_value(env, insn->src_reg)) { |
| verbose("R%d pointer comparison prohibited\n", |
| insn->src_reg); |
| return -EACCES; |
| } |
| } else { |
| if (insn->src_reg != BPF_REG_0) { |
| verbose("BPF_JMP uses reserved fields\n"); |
| return -EINVAL; |
| } |
| } |
| |
| /* check src2 operand */ |
| err = check_reg_arg(regs, insn->dst_reg, SRC_OP); |
| if (err) |
| return err; |
| |
| /* detect if R == 0 where R was initialized to zero earlier */ |
| if (BPF_SRC(insn->code) == BPF_K && |
| (opcode == BPF_JEQ || opcode == BPF_JNE) && |
| regs[insn->dst_reg].type == CONST_IMM && |
| regs[insn->dst_reg].imm == insn->imm) { |
| if (opcode == BPF_JEQ) { |
| /* if (imm == imm) goto pc+off; |
| * only follow the goto, ignore fall-through |
| */ |
| *insn_idx += insn->off; |
| return 0; |
| } else { |
| /* if (imm != imm) goto pc+off; |
| * only follow fall-through branch, since |
| * that's where the program will go |
| */ |
| return 0; |
| } |
| } |
| |
| other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx); |
| if (!other_branch) |
| return -EFAULT; |
| |
| /* detect if R == 0 where R is returned value from bpf_map_lookup_elem() */ |
| if (BPF_SRC(insn->code) == BPF_K && |
| insn->imm == 0 && (opcode == BPF_JEQ || |
| opcode == BPF_JNE) && |
| regs[insn->dst_reg].type == PTR_TO_MAP_VALUE_OR_NULL) { |
| if (opcode == BPF_JEQ) { |
| /* next fallthrough insn can access memory via |
| * this register |
| */ |
| regs[insn->dst_reg].type = PTR_TO_MAP_VALUE; |
| /* branch targer cannot access it, since reg == 0 */ |
| other_branch->regs[insn->dst_reg].type = CONST_IMM; |
| other_branch->regs[insn->dst_reg].imm = 0; |
| } else { |
| other_branch->regs[insn->dst_reg].type = PTR_TO_MAP_VALUE; |
| regs[insn->dst_reg].type = CONST_IMM; |
| regs[insn->dst_reg].imm = 0; |
| } |
| } else if (is_pointer_value(env, insn->dst_reg)) { |
| verbose("R%d pointer comparison prohibited\n", insn->dst_reg); |
| return -EACCES; |
| } else if (BPF_SRC(insn->code) == BPF_K && |
| (opcode == BPF_JEQ || opcode == BPF_JNE)) { |
| |
| if (opcode == BPF_JEQ) { |
| /* detect if (R == imm) goto |
| * and in the target state recognize that R = imm |
| */ |
| other_branch->regs[insn->dst_reg].type = CONST_IMM; |
| other_branch->regs[insn->dst_reg].imm = insn->imm; |
| } else { |
| /* detect if (R != imm) goto |
| * and in the fall-through state recognize that R = imm |
| */ |
| regs[insn->dst_reg].type = CONST_IMM; |
| regs[insn->dst_reg].imm = insn->imm; |
| } |
| } |
| if (log_level) |
| print_verifier_state(env); |
| return 0; |
| } |
| |
| /* return the map pointer stored inside BPF_LD_IMM64 instruction */ |
| static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn) |
| { |
| u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32; |
| |
| return (struct bpf_map *) (unsigned long) imm64; |
| } |
| |
| /* verify BPF_LD_IMM64 instruction */ |
| static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn) |
| { |
| struct reg_state *regs = env->cur_state.regs; |
| int err; |
| |
| if (BPF_SIZE(insn->code) != BPF_DW) { |
| verbose("invalid BPF_LD_IMM insn\n"); |
| return -EINVAL; |
| } |
| if (insn->off != 0) { |
| verbose("BPF_LD_IMM64 uses reserved fields\n"); |
| return -EINVAL; |
| } |
| |
| err = check_reg_arg(regs, insn->dst_reg, DST_OP); |
| if (err) |
| return err; |
| |
| if (insn->src_reg == 0) |
| /* generic move 64-bit immediate into a register */ |
| return 0; |
| |
| /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */ |
| BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD); |
| |
| regs[insn->dst_reg].type = CONST_PTR_TO_MAP; |
| regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn); |
| return 0; |
| } |
| |
| static bool may_access_skb(enum bpf_prog_type type) |
| { |
| switch (type) { |
| case BPF_PROG_TYPE_SOCKET_FILTER: |
| case BPF_PROG_TYPE_SCHED_CLS: |
| case BPF_PROG_TYPE_SCHED_ACT: |
| return true; |
| default: |
| return false; |
| } |
| } |
| |
| /* verify safety of LD_ABS|LD_IND instructions: |
| * - they can only appear in the programs where ctx == skb |
| * - since they are wrappers of function calls, they scratch R1-R5 registers, |
| * preserve R6-R9, and store return value into R0 |
| * |
| * Implicit input: |
| * ctx == skb == R6 == CTX |
| * |
| * Explicit input: |
| * SRC == any register |
| * IMM == 32-bit immediate |
| * |
| * Output: |
| * R0 - 8/16/32-bit skb data converted to cpu endianness |
| */ |
| static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn) |
| { |
| struct reg_state *regs = env->cur_state.regs; |
| u8 mode = BPF_MODE(insn->code); |
| struct reg_state *reg; |
| int i, err; |
| |
| if (!may_access_skb(env->prog->type)) { |
| verbose("BPF_LD_ABS|IND instructions not allowed for this program type\n"); |
| return -EINVAL; |
| } |
| |
| if (insn->dst_reg != BPF_REG_0 || insn->off != 0 || |
| (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) { |
| verbose("BPF_LD_ABS uses reserved fields\n"); |
| return -EINVAL; |
| } |
| |
| /* check whether implicit source operand (register R6) is readable */ |
| err = check_reg_arg(regs, BPF_REG_6, SRC_OP); |
| if (err) |
| return err; |
| |
| if (regs[BPF_REG_6].type != PTR_TO_CTX) { |
| verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n"); |
| return -EINVAL; |
| } |
| |
| if (mode == BPF_IND) { |
| /* check explicit source operand */ |
| err = check_reg_arg(regs, insn->src_reg, SRC_OP); |
| if (err) |
| return err; |
| } |
| |
| /* reset caller saved regs to unreadable */ |
| for (i = 0; i < CALLER_SAVED_REGS; i++) { |
| reg = regs + caller_saved[i]; |
| reg->type = NOT_INIT; |
| reg->imm = 0; |
| } |
| |
| /* mark destination R0 register as readable, since it contains |
| * the value fetched from the packet |
| */ |
| regs[BPF_REG_0].type = UNKNOWN_VALUE; |
| return 0; |
| } |
| |
| /* non-recursive DFS pseudo code |
| * 1 procedure DFS-iterative(G,v): |
| * 2 label v as discovered |
| * 3 let S be a stack |
| * 4 S.push(v) |
| * 5 while S is not empty |
| * 6 t <- S.pop() |
| * 7 if t is what we're looking for: |
| * 8 return t |
| * 9 for all edges e in G.adjacentEdges(t) do |
| * 10 if edge e is already labelled |
| * 11 continue with the next edge |
| * 12 w <- G.adjacentVertex(t,e) |
| * 13 if vertex w is not discovered and not explored |
| * 14 label e as tree-edge |
| * 15 label w as discovered |
| * 16 S.push(w) |
| * 17 continue at 5 |
| * 18 else if vertex w is discovered |
| * 19 label e as back-edge |
| * 20 else |
| * 21 // vertex w is explored |
| * 22 label e as forward- or cross-edge |
| * 23 label t as explored |
| * 24 S.pop() |
| * |
| * convention: |
| * 0x10 - discovered |
| * 0x11 - discovered and fall-through edge labelled |
| * 0x12 - discovered and fall-through and branch edges labelled |
| * 0x20 - explored |
| */ |
| |
| enum { |
| DISCOVERED = 0x10, |
| EXPLORED = 0x20, |
| FALLTHROUGH = 1, |
| BRANCH = 2, |
| }; |
| |
| #define STATE_LIST_MARK ((struct verifier_state_list *) -1L) |
| |
| static int *insn_stack; /* stack of insns to process */ |
| static int cur_stack; /* current stack index */ |
| static int *insn_state; |
| |
| /* t, w, e - match pseudo-code above: |
| * t - index of current instruction |
| * w - next instruction |
| * e - edge |
| */ |
| static int push_insn(int t, int w, int e, struct verifier_env *env) |
| { |
| if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH)) |
| return 0; |
| |
| if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH)) |
| return 0; |
| |
| if (w < 0 || w >= env->prog->len) { |
| verbose("jump out of range from insn %d to %d\n", t, w); |
| return -EINVAL; |
| } |
| |
| if (e == BRANCH) |
| /* mark branch target for state pruning */ |
| env->explored_states[w] = STATE_LIST_MARK; |
| |
| if (insn_state[w] == 0) { |
| /* tree-edge */ |
| insn_state[t] = DISCOVERED | e; |
| insn_state[w] = DISCOVERED; |
| if (cur_stack >= env->prog->len) |
| return -E2BIG; |
| insn_stack[cur_stack++] = w; |
| return 1; |
| } else if ((insn_state[w] & 0xF0) == DISCOVERED) { |
| verbose("back-edge from insn %d to %d\n", t, w); |
| return -EINVAL; |
| } else if (insn_state[w] == EXPLORED) { |
| /* forward- or cross-edge */ |
| insn_state[t] = DISCOVERED | e; |
| } else { |
| verbose("insn state internal bug\n"); |
| return -EFAULT; |
| } |
| return 0; |
| } |
| |
| /* non-recursive depth-first-search to detect loops in BPF program |
| * loop == back-edge in directed graph |
| */ |
| static int check_cfg(struct verifier_env *env) |
| { |
| struct bpf_insn *insns = env->prog->insnsi; |
| int insn_cnt = env->prog->len; |
| int ret = 0; |
| int i, t; |
| |
| insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); |
| if (!insn_state) |
| return -ENOMEM; |
| |
| insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); |
| if (!insn_stack) { |
| kfree(insn_state); |
| return -ENOMEM; |
| } |
| |
| insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */ |
| insn_stack[0] = 0; /* 0 is the first instruction */ |
| cur_stack = 1; |
| |
| peek_stack: |
| if (cur_stack == 0) |
| goto check_state; |
| t = insn_stack[cur_stack - 1]; |
| |
| if (BPF_CLASS(insns[t].code) == BPF_JMP) { |
| u8 opcode = BPF_OP(insns[t].code); |
| |
| if (opcode == BPF_EXIT) { |
| goto mark_explored; |
| } else if (opcode == BPF_CALL) { |
| ret = push_insn(t, t + 1, FALLTHROUGH, env); |
| if (ret == 1) |
| goto peek_stack; |
| else if (ret < 0) |
| goto err_free; |
| if (t + 1 < insn_cnt) |
| env->explored_states[t + 1] = STATE_LIST_MARK; |
| } else if (opcode == BPF_JA) { |
| if (BPF_SRC(insns[t].code) != BPF_K) { |
| ret = -EINVAL; |
| goto err_free; |
| } |
| /* unconditional jump with single edge */ |
| ret = push_insn(t, t + insns[t].off + 1, |
| FALLTHROUGH, env); |
| if (ret == 1) |
| goto peek_stack; |
| else if (ret < 0) |
| goto err_free; |
| /* tell verifier to check for equivalent states |
| * after every call and jump |
| */ |
| if (t + 1 < insn_cnt) |
| env->explored_states[t + 1] = STATE_LIST_MARK; |
| } else { |
| /* conditional jump with two edges */ |
| ret = push_insn(t, t + 1, FALLTHROUGH, env); |
| if (ret == 1) |
| goto peek_stack; |
| else if (ret < 0) |
| goto err_free; |
| |
| ret = push_insn(t, t + insns[t].off + 1, BRANCH, env); |
| if (ret == 1) |
| goto peek_stack; |
| else if (ret < 0) |
| goto err_free; |
| } |
| } else { |
| /* all other non-branch instructions with single |
| * fall-through edge |
| */ |
| ret = push_insn(t, t + 1, FALLTHROUGH, env); |
| if (ret == 1) |
| goto peek_stack; |
| else if (ret < 0) |
| goto err_free; |
| } |
| |
| mark_explored: |
| insn_state[t] = EXPLORED; |
| if (cur_stack-- <= 0) { |
| verbose("pop stack internal bug\n"); |
| ret = -EFAULT; |
| goto err_free; |
| } |
| goto peek_stack; |
| |
| check_state: |
| for (i = 0; i < insn_cnt; i++) { |
| if (insn_state[i] != EXPLORED) { |
| verbose("unreachable insn %d\n", i); |
| ret = -EINVAL; |
| goto err_free; |
| } |
| } |
| ret = 0; /* cfg looks good */ |
| |
| err_free: |
| kfree(insn_state); |
| kfree(insn_stack); |
| return ret; |
| } |
| |
| /* compare two verifier states |
| * |
| * all states stored in state_list are known to be valid, since |
| * verifier reached 'bpf_exit' instruction through them |
| * |
| * this function is called when verifier exploring different branches of |
| * execution popped from the state stack. If it sees an old state that has |
| * more strict register state and more strict stack state then this execution |
| * branch doesn't need to be explored further, since verifier already |
| * concluded that more strict state leads to valid finish. |
| * |
| * Therefore two states are equivalent if register state is more conservative |
| * and explored stack state is more conservative than the current one. |
| * Example: |
| * explored current |
| * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC) |
| * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC) |
| * |
| * In other words if current stack state (one being explored) has more |
| * valid slots than old one that already passed validation, it means |
| * the verifier can stop exploring and conclude that current state is valid too |
| * |
| * Similarly with registers. If explored state has register type as invalid |
| * whereas register type in current state is meaningful, it means that |
| * the current state will reach 'bpf_exit' instruction safely |
| */ |
| static bool states_equal(struct verifier_state *old, struct verifier_state *cur) |
| { |
| int i; |
| |
| for (i = 0; i < MAX_BPF_REG; i++) { |
| if (memcmp(&old->regs[i], &cur->regs[i], |
| sizeof(old->regs[0])) != 0) { |
| if (old->regs[i].type == NOT_INIT || |
| (old->regs[i].type == UNKNOWN_VALUE && |
| cur->regs[i].type != NOT_INIT)) |
| continue; |
| return false; |
| } |
| } |
| |
| for (i = 0; i < MAX_BPF_STACK; i++) { |
| if (old->stack_slot_type[i] == STACK_INVALID) |
| continue; |
| if (old->stack_slot_type[i] != cur->stack_slot_type[i]) |
| /* Ex: old explored (safe) state has STACK_SPILL in |
| * this stack slot, but current has has STACK_MISC -> |
| * this verifier states are not equivalent, |
| * return false to continue verification of this path |
| */ |
| return false; |
| if (i % BPF_REG_SIZE) |
| continue; |
| if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE], |
| &cur->spilled_regs[i / BPF_REG_SIZE], |
| sizeof(old->spilled_regs[0]))) |
| /* when explored and current stack slot types are |
| * the same, check that stored pointers types |
| * are the same as well. |
| * Ex: explored safe path could have stored |
| * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8} |
| * but current path has stored: |
| * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16} |
| * such verifier states are not equivalent. |
| * return false to continue verification of this path |
| */ |
| return false; |
| else |
| continue; |
| } |
| return true; |
| } |
| |
| static int is_state_visited(struct verifier_env *env, int insn_idx) |
| { |
| struct verifier_state_list *new_sl; |
| struct verifier_state_list *sl; |
| |
| sl = env->explored_states[insn_idx]; |
| if (!sl) |
| /* this 'insn_idx' instruction wasn't marked, so we will not |
| * be doing state search here |
| */ |
| return 0; |
| |
| while (sl != STATE_LIST_MARK) { |
| if (states_equal(&sl->state, &env->cur_state)) |
| /* reached equivalent register/stack state, |
| * prune the search |
| */ |
| return 1; |
| sl = sl->next; |
| } |
| |
| /* there were no equivalent states, remember current one. |
| * technically the current state is not proven to be safe yet, |
| * but it will either reach bpf_exit (which means it's safe) or |
| * it will be rejected. Since there are no loops, we won't be |
| * seeing this 'insn_idx' instruction again on the way to bpf_exit |
| */ |
| new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER); |
| if (!new_sl) |
| return -ENOMEM; |
| |
| /* add new state to the head of linked list */ |
| memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state)); |
| new_sl->next = env->explored_states[insn_idx]; |
| env->explored_states[insn_idx] = new_sl; |
| return 0; |
| } |
| |
| static int do_check(struct verifier_env *env) |
| { |
| struct verifier_state *state = &env->cur_state; |
| struct bpf_insn *insns = env->prog->insnsi; |
| struct reg_state *regs = state->regs; |
| int insn_cnt = env->prog->len; |
| int insn_idx, prev_insn_idx = 0; |
| int insn_processed = 0; |
| bool do_print_state = false; |
| |
| init_reg_state(regs); |
| insn_idx = 0; |
| for (;;) { |
| struct bpf_insn *insn; |
| u8 class; |
| int err; |
| |
| if (insn_idx >= insn_cnt) { |
| verbose("invalid insn idx %d insn_cnt %d\n", |
| insn_idx, insn_cnt); |
| return -EFAULT; |
| } |
| |
| insn = &insns[insn_idx]; |
| class = BPF_CLASS(insn->code); |
| |
| if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) { |
| verbose("BPF program is too large. Proccessed %d insn\n", |
| insn_processed); |
| return -E2BIG; |
| } |
| |
| err = is_state_visited(env, insn_idx); |
| if (err < 0) |
| return err; |
| if (err == 1) { |
| /* found equivalent state, can prune the search */ |
| if (log_level) { |
| if (do_print_state) |
| verbose("\nfrom %d to %d: safe\n", |
| prev_insn_idx, insn_idx); |
| else |
| verbose("%d: safe\n", insn_idx); |
| } |
| goto process_bpf_exit; |
| } |
| |
| if (log_level && do_print_state) { |
| verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx); |
| print_verifier_state(env); |
| do_print_state = false; |
| } |
| |
| if (log_level) { |
| verbose("%d: ", insn_idx); |
| print_bpf_insn(insn); |
| } |
| |
| if (class == BPF_ALU || class == BPF_ALU64) { |
| err = check_alu_op(env, insn); |
| if (err) |
| return err; |
| |
| } else if (class == BPF_LDX) { |
| enum bpf_reg_type src_reg_type; |
| |
| /* check for reserved fields is already done */ |
| |
| /* check src operand */ |
| err = check_reg_arg(regs, insn->src_reg, SRC_OP); |
| if (err) |
| return err; |
| |
| err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); |
| if (err) |
| return err; |
| |
| src_reg_type = regs[insn->src_reg].type; |
| |
| /* check that memory (src_reg + off) is readable, |
| * the state of dst_reg will be updated by this func |
| */ |
| err = check_mem_access(env, insn->src_reg, insn->off, |
| BPF_SIZE(insn->code), BPF_READ, |
| insn->dst_reg); |
| if (err) |
| return err; |
| |
| if (BPF_SIZE(insn->code) != BPF_W) { |
| insn_idx++; |
| continue; |
| } |
| |
| if (insn->imm == 0) { |
| /* saw a valid insn |
| * dst_reg = *(u32 *)(src_reg + off) |
| * use reserved 'imm' field to mark this insn |
| */ |
| insn->imm = src_reg_type; |
| |
| } else if (src_reg_type != insn->imm && |
| (src_reg_type == PTR_TO_CTX || |
| insn->imm == PTR_TO_CTX)) { |
| /* ABuser program is trying to use the same insn |
| * dst_reg = *(u32*) (src_reg + off) |
| * with different pointer types: |
| * src_reg == ctx in one branch and |
| * src_reg == stack|map in some other branch. |
| * Reject it. |
| */ |
| verbose("same insn cannot be used with different pointers\n"); |
| return -EINVAL; |
| } |
| |
| } else if (class == BPF_STX) { |
| enum bpf_reg_type dst_reg_type; |
| |
| if (BPF_MODE(insn->code) == BPF_XADD) { |
| err = check_xadd(env, insn); |
| if (err) |
| return err; |
| insn_idx++; |
| continue; |
| } |
| |
| /* check src1 operand */ |
| err = check_reg_arg(regs, insn->src_reg, SRC_OP); |
| if (err) |
| return err; |
| /* check src2 operand */ |
| err = check_reg_arg(regs, insn->dst_reg, SRC_OP); |
| if (err) |
| return err; |
| |
| dst_reg_type = regs[insn->dst_reg].type; |
| |
| /* check that memory (dst_reg + off) is writeable */ |
| err = check_mem_access(env, insn->dst_reg, insn->off, |
| BPF_SIZE(insn->code), BPF_WRITE, |
| insn->src_reg); |
| if (err) |
| return err; |
| |
| if (insn->imm == 0) { |
| insn->imm = dst_reg_type; |
| } else if (dst_reg_type != insn->imm && |
| (dst_reg_type == PTR_TO_CTX || |
| insn->imm == PTR_TO_CTX)) { |
| verbose("same insn cannot be used with different pointers\n"); |
| return -EINVAL; |
| } |
| |
| } else if (class == BPF_ST) { |
| if (BPF_MODE(insn->code) != BPF_MEM || |
| insn->src_reg != BPF_REG_0) { |
| verbose("BPF_ST uses reserved fields\n"); |
| return -EINVAL; |
| } |
| /* check src operand */ |
| err = check_reg_arg(regs, insn->dst_reg, SRC_OP); |
| if (err) |
| return err; |
| |
| /* check that memory (dst_reg + off) is writeable */ |
| err = check_mem_access(env, insn->dst_reg, insn->off, |
| BPF_SIZE(insn->code), BPF_WRITE, |
| -1); |
| if (err) |
| return err; |
| |
| } else if (class == BPF_JMP) { |
| u8 opcode = BPF_OP(insn->code); |
| |
| if (opcode == BPF_CALL) { |
| if (BPF_SRC(insn->code) != BPF_K || |
| insn->off != 0 || |
| insn->src_reg != BPF_REG_0 || |
| insn->dst_reg != BPF_REG_0) { |
| verbose("BPF_CALL uses reserved fields\n"); |
| return -EINVAL; |
| } |
| |
| err = check_call(env, insn->imm); |
| if (err) |
| return err; |
| |
| } else if (opcode == BPF_JA) { |
| if (BPF_SRC(insn->code) != BPF_K || |
| insn->imm != 0 || |
| insn->src_reg != BPF_REG_0 || |
| insn->dst_reg != BPF_REG_0) { |
| verbose("BPF_JA uses reserved fields\n"); |
| return -EINVAL; |
| } |
| |
| insn_idx += insn->off + 1; |
| continue; |
| |
| } else if (opcode == BPF_EXIT) { |
| if (BPF_SRC(insn->code) != BPF_K || |
| insn->imm != 0 || |
| insn->src_reg != BPF_REG_0 || |
| insn->dst_reg != BPF_REG_0) { |
| verbose("BPF_EXIT uses reserved fields\n"); |
| return -EINVAL; |
| } |
| |
| /* eBPF calling convetion is such that R0 is used |
| * to return the value from eBPF program. |
| * Make sure that it's readable at this time |
| * of bpf_exit, which means that program wrote |
| * something into it earlier |
| */ |
| err = check_reg_arg(regs, BPF_REG_0, SRC_OP); |
| if (err) |
| return err; |
| |
| if (is_pointer_value(env, BPF_REG_0)) { |
| verbose("R0 leaks addr as return value\n"); |
| return -EACCES; |
| } |
| |
| process_bpf_exit: |
| insn_idx = pop_stack(env, &prev_insn_idx); |
| if (insn_idx < 0) { |
| break; |
| } else { |
| do_print_state = true; |
| continue; |
| } |
| } else { |
| err = check_cond_jmp_op(env, insn, &insn_idx); |
| if (err) |
| return err; |
| } |
| } else if (class == BPF_LD) { |
| u8 mode = BPF_MODE(insn->code); |
| |
| if (mode == BPF_ABS || mode == BPF_IND) { |
| err = check_ld_abs(env, insn); |
| if (err) |
| return err; |
| |
| } else if (mode == BPF_IMM) { |
| err = check_ld_imm(env, insn); |
| if (err) |
| return err; |
| |
| insn_idx++; |
| } else { |
| verbose("invalid BPF_LD mode\n"); |
| return -EINVAL; |
| } |
| } else { |
| verbose("unknown insn class %d\n", class); |
| return -EINVAL; |
| } |
| |
| insn_idx++; |
| } |
| |
| return 0; |
| } |
| |
| /* look for pseudo eBPF instructions that access map FDs and |
| * replace them with actual map pointers |
| */ |
| static int replace_map_fd_with_map_ptr(struct verifier_env *env) |
| { |
| struct bpf_insn *insn = env->prog->insnsi; |
| int insn_cnt = env->prog->len; |
| int i, j; |
| |
| for (i = 0; i < insn_cnt; i++, insn++) { |
| if (BPF_CLASS(insn->code) == BPF_LDX && |
| (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) { |
| verbose("BPF_LDX uses reserved fields\n"); |
| return -EINVAL; |
| } |
| |
| if (BPF_CLASS(insn->code) == BPF_STX && |
| ((BPF_MODE(insn->code) != BPF_MEM && |
| BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) { |
| verbose("BPF_STX uses reserved fields\n"); |
| return -EINVAL; |
| } |
| |
| if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) { |
| struct bpf_map *map; |
| struct fd f; |
| |
| if (i == insn_cnt - 1 || insn[1].code != 0 || |
| insn[1].dst_reg != 0 || insn[1].src_reg != 0 || |
| insn[1].off != 0) { |
| verbose("invalid bpf_ld_imm64 insn\n"); |
| return -EINVAL; |
| } |
| |
| if (insn->src_reg == 0) |
| /* valid generic load 64-bit imm */ |
| goto next_insn; |
| |
| if (insn->src_reg != BPF_PSEUDO_MAP_FD) { |
| verbose("unrecognized bpf_ld_imm64 insn\n"); |
| return -EINVAL; |
| } |
| |
| f = fdget(insn->imm); |
| map = __bpf_map_get(f); |
| if (IS_ERR(map)) { |
| verbose("fd %d is not pointing to valid bpf_map\n", |
| insn->imm); |
| fdput(f); |
| return PTR_ERR(map); |
| } |
| |
| /* store map pointer inside BPF_LD_IMM64 instruction */ |
| insn[0].imm = (u32) (unsigned long) map; |
| insn[1].imm = ((u64) (unsigned long) map) >> 32; |
| |
| /* check whether we recorded this map already */ |
| for (j = 0; j < env->used_map_cnt; j++) |
| if (env->used_maps[j] == map) { |
| fdput(f); |
| goto next_insn; |
| } |
| |
| if (env->used_map_cnt >= MAX_USED_MAPS) { |
| fdput(f); |
| return -E2BIG; |
| } |
| |
| /* remember this map */ |
| env->used_maps[env->used_map_cnt++] = map; |
| |
| /* hold the map. If the program is rejected by verifier, |
| * the map will be released by release_maps() or it |
| * will be used by the valid program until it's unloaded |
| * and all maps are released in free_bpf_prog_info() |
| */ |
| bpf_map_inc(map, false); |
| fdput(f); |
| next_insn: |
| insn++; |
| i++; |
| } |
| } |
| |
| /* now all pseudo BPF_LD_IMM64 instructions load valid |
| * 'struct bpf_map *' into a register instead of user map_fd. |
| * These pointers will be used later by verifier to validate map access. |
| */ |
| return 0; |
| } |
| |
| /* drop refcnt of maps used by the rejected program */ |
| static void release_maps(struct verifier_env *env) |
| { |
| int i; |
| |
| for (i = 0; i < env->used_map_cnt; i++) |
| bpf_map_put(env->used_maps[i]); |
| } |
| |
| /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */ |
| static void convert_pseudo_ld_imm64(struct verifier_env *env) |
| { |
| struct bpf_insn *insn = env->prog->insnsi; |
| int insn_cnt = env->prog->len; |
| int i; |
| |
| for (i = 0; i < insn_cnt; i++, insn++) |
| if (insn->code == (BPF_LD | BPF_IMM | BPF_DW)) |
| insn->src_reg = 0; |
| } |
| |
| static void adjust_branches(struct bpf_prog *prog, int pos, int delta) |
| { |
| struct bpf_insn *insn = prog->insnsi; |
| int insn_cnt = prog->len; |
| int i; |
| |
| for (i = 0; i < insn_cnt; i++, insn++) { |
| if (BPF_CLASS(insn->code) != BPF_JMP || |
| BPF_OP(insn->code) == BPF_CALL || |
| BPF_OP(insn->code) == BPF_EXIT) |
| continue; |
| |
| /* adjust offset of jmps if necessary */ |
| if (i < pos && i + insn->off + 1 > pos) |
| insn->off += delta; |
| else if (i > pos + delta && i + insn->off + 1 <= pos + delta) |
| insn->off -= delta; |
| } |
| } |
| |
| /* convert load instructions that access fields of 'struct __sk_buff' |
| * into sequence of instructions that access fields of 'struct sk_buff' |
| */ |
| static int convert_ctx_accesses(struct verifier_env *env) |
| { |
| struct bpf_insn *insn = env->prog->insnsi; |
| int insn_cnt = env->prog->len; |
| struct bpf_insn insn_buf[16]; |
| struct bpf_prog *new_prog; |
| u32 cnt; |
| int i; |
| enum bpf_access_type type; |
| |
| if (!env->prog->aux->ops->convert_ctx_access) |
| return 0; |
| |
| for (i = 0; i < insn_cnt; i++, insn++) { |
| if (insn->code == (BPF_LDX | BPF_MEM | BPF_W)) |
| type = BPF_READ; |
| else if (insn->code == (BPF_STX | BPF_MEM | BPF_W)) |
| type = BPF_WRITE; |
| else |
| continue; |
| |
| if (insn->imm != PTR_TO_CTX) { |
| /* clear internal mark */ |
| insn->imm = 0; |
| continue; |
| } |
| |
| cnt = env->prog->aux->ops-> |
| convert_ctx_access(type, insn->dst_reg, insn->src_reg, |
| insn->off, insn_buf, env->prog); |
| if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) { |
| verbose("bpf verifier is misconfigured\n"); |
| return -EINVAL; |
| } |
| |
| if (cnt == 1) { |
| memcpy(insn, insn_buf, sizeof(*insn)); |
| continue; |
| } |
| |
| /* several new insns need to be inserted. Make room for them */ |
| insn_cnt += cnt - 1; |
| new_prog = bpf_prog_realloc(env->prog, |
| bpf_prog_size(insn_cnt), |
| GFP_USER); |
| if (!new_prog) |
| return -ENOMEM; |
| |
| new_prog->len = insn_cnt; |
| |
| memmove(new_prog->insnsi + i + cnt, new_prog->insns + i + 1, |
| sizeof(*insn) * (insn_cnt - i - cnt)); |
| |
| /* copy substitute insns in place of load instruction */ |
| memcpy(new_prog->insnsi + i, insn_buf, sizeof(*insn) * cnt); |
| |
| /* adjust branches in the whole program */ |
| adjust_branches(new_prog, i, cnt - 1); |
| |
| /* keep walking new program and skip insns we just inserted */ |
| env->prog = new_prog; |
| insn = new_prog->insnsi + i + cnt - 1; |
| i += cnt - 1; |
| } |
| |
| return 0; |
| } |
| |
| static void free_states(struct verifier_env *env) |
| { |
| struct verifier_state_list *sl, *sln; |
| int i; |
| |
| if (!env->explored_states) |
| return; |
| |
| for (i = 0; i < env->prog->len; i++) { |
| sl = env->explored_states[i]; |
| |
| if (sl) |
| while (sl != STATE_LIST_MARK) { |
| sln = sl->next; |
| kfree(sl); |
| sl = sln; |
| } |
| } |
| |
| kfree(env->explored_states); |
| } |
| |
| int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) |
| { |
| char __user *log_ubuf = NULL; |
| struct verifier_env *env; |
| int ret = -EINVAL; |
| |
| if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS) |
| return -E2BIG; |
| |
| /* 'struct verifier_env' can be global, but since it's not small, |
| * allocate/free it every time bpf_check() is called |
| */ |
| env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL); |
| if (!env) |
| return -ENOMEM; |
| |
| env->prog = *prog; |
| |
| /* grab the mutex to protect few globals used by verifier */ |
| mutex_lock(&bpf_verifier_lock); |
| |
| if (attr->log_level || attr->log_buf || attr->log_size) { |
| /* user requested verbose verifier output |
| * and supplied buffer to store the verification trace |
| */ |
| log_level = attr->log_level; |
| log_ubuf = (char __user *) (unsigned long) attr->log_buf; |
| log_size = attr->log_size; |
| log_len = 0; |
| |
| ret = -EINVAL; |
| /* log_* values have to be sane */ |
| if (log_size < 128 || log_size > UINT_MAX >> 8 || |
| log_level == 0 || log_ubuf == NULL) |
| goto free_env; |
| |
| ret = -ENOMEM; |
| log_buf = vmalloc(log_size); |
| if (!log_buf) |
| goto free_env; |
| } else { |
| log_level = 0; |
| } |
| |
| ret = replace_map_fd_with_map_ptr(env); |
| if (ret < 0) |
| goto skip_full_check; |
| |
| env->explored_states = kcalloc(env->prog->len, |
| sizeof(struct verifier_state_list *), |
| GFP_USER); |
| ret = -ENOMEM; |
| if (!env->explored_states) |
| goto skip_full_check; |
| |
| ret = check_cfg(env); |
| if (ret < 0) |
| goto skip_full_check; |
| |
| env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); |
| |
| ret = do_check(env); |
| |
| skip_full_check: |
| while (pop_stack(env, NULL) >= 0); |
| free_states(env); |
| |
| if (ret == 0) |
| /* program is valid, convert *(u32*)(ctx + off) accesses */ |
| ret = convert_ctx_accesses(env); |
| |
| if (log_level && log_len >= log_size - 1) { |
| BUG_ON(log_len >= log_size); |
| /* verifier log exceeded user supplied buffer */ |
| ret = -ENOSPC; |
| /* fall through to return what was recorded */ |
| } |
| |
| /* copy verifier log back to user space including trailing zero */ |
| if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) { |
| ret = -EFAULT; |
| goto free_log_buf; |
| } |
| |
| if (ret == 0 && env->used_map_cnt) { |
| /* if program passed verifier, update used_maps in bpf_prog_info */ |
| env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt, |
| sizeof(env->used_maps[0]), |
| GFP_KERNEL); |
| |
| if (!env->prog->aux->used_maps) { |
| ret = -ENOMEM; |
| goto free_log_buf; |
| } |
| |
| memcpy(env->prog->aux->used_maps, env->used_maps, |
| sizeof(env->used_maps[0]) * env->used_map_cnt); |
| env->prog->aux->used_map_cnt = env->used_map_cnt; |
| |
| /* program is valid. Convert pseudo bpf_ld_imm64 into generic |
| * bpf_ld_imm64 instructions |
| */ |
| convert_pseudo_ld_imm64(env); |
| } |
| |
| free_log_buf: |
| if (log_level) |
| vfree(log_buf); |
| free_env: |
| if (!env->prog->aux->used_maps) |
| /* if we didn't copy map pointers into bpf_prog_info, release |
| * them now. Otherwise free_bpf_prog_info() will release them. |
| */ |
| release_maps(env); |
| *prog = env->prog; |
| kfree(env); |
| mutex_unlock(&bpf_verifier_lock); |
| return ret; |
| } |