| /* |
| * linux/kernel/seccomp.c |
| * |
| * Copyright 2004-2005 Andrea Arcangeli <andrea@cpushare.com> |
| * |
| * Copyright (C) 2012 Google, Inc. |
| * Will Drewry <wad@chromium.org> |
| * |
| * This defines a simple but solid secure-computing facility. |
| * |
| * Mode 1 uses a fixed list of allowed system calls. |
| * Mode 2 allows user-defined system call filters in the form |
| * of Berkeley Packet Filters/Linux Socket Filters. |
| */ |
| |
| #include <linux/atomic.h> |
| #include <linux/audit.h> |
| #include <linux/compat.h> |
| #include <linux/coredump.h> |
| #include <linux/sched.h> |
| #include <linux/seccomp.h> |
| #include <linux/slab.h> |
| #include <linux/syscalls.h> |
| |
| #ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER |
| #include <asm/syscall.h> |
| #endif |
| |
| #ifdef CONFIG_SECCOMP_FILTER |
| #include <linux/filter.h> |
| #include <linux/pid.h> |
| #include <linux/ptrace.h> |
| #include <linux/security.h> |
| #include <linux/tracehook.h> |
| #include <linux/uaccess.h> |
| |
| /** |
| * struct seccomp_filter - container for seccomp BPF programs |
| * |
| * @usage: reference count to manage the object lifetime. |
| * get/put helpers should be used when accessing an instance |
| * outside of a lifetime-guarded section. In general, this |
| * is only needed for handling filters shared across tasks. |
| * @prev: points to a previously installed, or inherited, filter |
| * @prog: the BPF program to evaluate |
| * |
| * seccomp_filter objects are organized in a tree linked via the @prev |
| * pointer. For any task, it appears to be a singly-linked list starting |
| * with current->seccomp.filter, the most recently attached or inherited filter. |
| * However, multiple filters may share a @prev node, by way of fork(), which |
| * results in a unidirectional tree existing in memory. This is similar to |
| * how namespaces work. |
| * |
| * seccomp_filter objects should never be modified after being attached |
| * to a task_struct (other than @usage). |
| */ |
| struct seccomp_filter { |
| atomic_t usage; |
| struct seccomp_filter *prev; |
| struct bpf_prog *prog; |
| }; |
| |
| /* Limit any path through the tree to 256KB worth of instructions. */ |
| #define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter)) |
| |
| /* |
| * Endianness is explicitly ignored and left for BPF program authors to manage |
| * as per the specific architecture. |
| */ |
| static void populate_seccomp_data(struct seccomp_data *sd) |
| { |
| struct task_struct *task = current; |
| struct pt_regs *regs = task_pt_regs(task); |
| unsigned long args[6]; |
| |
| sd->nr = syscall_get_nr(task, regs); |
| sd->arch = syscall_get_arch(); |
| syscall_get_arguments(task, regs, 0, 6, args); |
| sd->args[0] = args[0]; |
| sd->args[1] = args[1]; |
| sd->args[2] = args[2]; |
| sd->args[3] = args[3]; |
| sd->args[4] = args[4]; |
| sd->args[5] = args[5]; |
| sd->instruction_pointer = KSTK_EIP(task); |
| } |
| |
| /** |
| * seccomp_check_filter - verify seccomp filter code |
| * @filter: filter to verify |
| * @flen: length of filter |
| * |
| * Takes a previously checked filter (by bpf_check_classic) and |
| * redirects all filter code that loads struct sk_buff data |
| * and related data through seccomp_bpf_load. It also |
| * enforces length and alignment checking of those loads. |
| * |
| * Returns 0 if the rule set is legal or -EINVAL if not. |
| */ |
| static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen) |
| { |
| int pc; |
| for (pc = 0; pc < flen; pc++) { |
| struct sock_filter *ftest = &filter[pc]; |
| u16 code = ftest->code; |
| u32 k = ftest->k; |
| |
| switch (code) { |
| case BPF_LD | BPF_W | BPF_ABS: |
| ftest->code = BPF_LDX | BPF_W | BPF_ABS; |
| /* 32-bit aligned and not out of bounds. */ |
| if (k >= sizeof(struct seccomp_data) || k & 3) |
| return -EINVAL; |
| continue; |
| case BPF_LD | BPF_W | BPF_LEN: |
| ftest->code = BPF_LD | BPF_IMM; |
| ftest->k = sizeof(struct seccomp_data); |
| continue; |
| case BPF_LDX | BPF_W | BPF_LEN: |
| ftest->code = BPF_LDX | BPF_IMM; |
| ftest->k = sizeof(struct seccomp_data); |
| continue; |
| /* Explicitly include allowed calls. */ |
| case BPF_RET | BPF_K: |
| case BPF_RET | BPF_A: |
| case BPF_ALU | BPF_ADD | BPF_K: |
| case BPF_ALU | BPF_ADD | BPF_X: |
| case BPF_ALU | BPF_SUB | BPF_K: |
| case BPF_ALU | BPF_SUB | BPF_X: |
| case BPF_ALU | BPF_MUL | BPF_K: |
| case BPF_ALU | BPF_MUL | BPF_X: |
| case BPF_ALU | BPF_DIV | BPF_K: |
| case BPF_ALU | BPF_DIV | BPF_X: |
| case BPF_ALU | BPF_AND | BPF_K: |
| case BPF_ALU | BPF_AND | BPF_X: |
| case BPF_ALU | BPF_OR | BPF_K: |
| case BPF_ALU | BPF_OR | BPF_X: |
| case BPF_ALU | BPF_XOR | BPF_K: |
| case BPF_ALU | BPF_XOR | BPF_X: |
| case BPF_ALU | BPF_LSH | BPF_K: |
| case BPF_ALU | BPF_LSH | BPF_X: |
| case BPF_ALU | BPF_RSH | BPF_K: |
| case BPF_ALU | BPF_RSH | BPF_X: |
| case BPF_ALU | BPF_NEG: |
| case BPF_LD | BPF_IMM: |
| case BPF_LDX | BPF_IMM: |
| case BPF_MISC | BPF_TAX: |
| case BPF_MISC | BPF_TXA: |
| case BPF_LD | BPF_MEM: |
| case BPF_LDX | BPF_MEM: |
| case BPF_ST: |
| case BPF_STX: |
| case BPF_JMP | BPF_JA: |
| case BPF_JMP | BPF_JEQ | BPF_K: |
| case BPF_JMP | BPF_JEQ | BPF_X: |
| case BPF_JMP | BPF_JGE | BPF_K: |
| case BPF_JMP | BPF_JGE | BPF_X: |
| case BPF_JMP | BPF_JGT | BPF_K: |
| case BPF_JMP | BPF_JGT | BPF_X: |
| case BPF_JMP | BPF_JSET | BPF_K: |
| case BPF_JMP | BPF_JSET | BPF_X: |
| continue; |
| default: |
| return -EINVAL; |
| } |
| } |
| return 0; |
| } |
| |
| /** |
| * seccomp_run_filters - evaluates all seccomp filters against @sd |
| * @sd: optional seccomp data to be passed to filters |
| * |
| * Returns valid seccomp BPF response codes. |
| */ |
| static u32 seccomp_run_filters(const struct seccomp_data *sd) |
| { |
| struct seccomp_data sd_local; |
| u32 ret = SECCOMP_RET_ALLOW; |
| /* Make sure cross-thread synced filter points somewhere sane. */ |
| struct seccomp_filter *f = |
| lockless_dereference(current->seccomp.filter); |
| |
| /* Ensure unexpected behavior doesn't result in failing open. */ |
| if (unlikely(WARN_ON(f == NULL))) |
| return SECCOMP_RET_KILL; |
| |
| if (!sd) { |
| populate_seccomp_data(&sd_local); |
| sd = &sd_local; |
| } |
| |
| /* |
| * All filters in the list are evaluated and the lowest BPF return |
| * value always takes priority (ignoring the DATA). |
| */ |
| for (; f; f = f->prev) { |
| u32 cur_ret = BPF_PROG_RUN(f->prog, sd); |
| |
| if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION)) |
| ret = cur_ret; |
| } |
| return ret; |
| } |
| #endif /* CONFIG_SECCOMP_FILTER */ |
| |
| static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode) |
| { |
| assert_spin_locked(¤t->sighand->siglock); |
| |
| if (current->seccomp.mode && current->seccomp.mode != seccomp_mode) |
| return false; |
| |
| return true; |
| } |
| |
| static inline void seccomp_assign_mode(struct task_struct *task, |
| unsigned long seccomp_mode) |
| { |
| assert_spin_locked(&task->sighand->siglock); |
| |
| task->seccomp.mode = seccomp_mode; |
| /* |
| * Make sure TIF_SECCOMP cannot be set before the mode (and |
| * filter) is set. |
| */ |
| smp_mb__before_atomic(); |
| set_tsk_thread_flag(task, TIF_SECCOMP); |
| } |
| |
| #ifdef CONFIG_SECCOMP_FILTER |
| /* Returns 1 if the parent is an ancestor of the child. */ |
| static int is_ancestor(struct seccomp_filter *parent, |
| struct seccomp_filter *child) |
| { |
| /* NULL is the root ancestor. */ |
| if (parent == NULL) |
| return 1; |
| for (; child; child = child->prev) |
| if (child == parent) |
| return 1; |
| return 0; |
| } |
| |
| /** |
| * seccomp_can_sync_threads: checks if all threads can be synchronized |
| * |
| * Expects sighand and cred_guard_mutex locks to be held. |
| * |
| * Returns 0 on success, -ve on error, or the pid of a thread which was |
| * either not in the correct seccomp mode or it did not have an ancestral |
| * seccomp filter. |
| */ |
| static inline pid_t seccomp_can_sync_threads(void) |
| { |
| struct task_struct *thread, *caller; |
| |
| BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); |
| assert_spin_locked(¤t->sighand->siglock); |
| |
| /* Validate all threads being eligible for synchronization. */ |
| caller = current; |
| for_each_thread(caller, thread) { |
| pid_t failed; |
| |
| /* Skip current, since it is initiating the sync. */ |
| if (thread == caller) |
| continue; |
| |
| if (thread->seccomp.mode == SECCOMP_MODE_DISABLED || |
| (thread->seccomp.mode == SECCOMP_MODE_FILTER && |
| is_ancestor(thread->seccomp.filter, |
| caller->seccomp.filter))) |
| continue; |
| |
| /* Return the first thread that cannot be synchronized. */ |
| failed = task_pid_vnr(thread); |
| /* If the pid cannot be resolved, then return -ESRCH */ |
| if (unlikely(WARN_ON(failed == 0))) |
| failed = -ESRCH; |
| return failed; |
| } |
| |
| return 0; |
| } |
| |
| /** |
| * seccomp_sync_threads: sets all threads to use current's filter |
| * |
| * Expects sighand and cred_guard_mutex locks to be held, and for |
| * seccomp_can_sync_threads() to have returned success already |
| * without dropping the locks. |
| * |
| */ |
| static inline void seccomp_sync_threads(void) |
| { |
| struct task_struct *thread, *caller; |
| |
| BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); |
| assert_spin_locked(¤t->sighand->siglock); |
| |
| /* Synchronize all threads. */ |
| caller = current; |
| for_each_thread(caller, thread) { |
| /* Skip current, since it needs no changes. */ |
| if (thread == caller) |
| continue; |
| |
| /* Get a task reference for the new leaf node. */ |
| get_seccomp_filter(caller); |
| /* |
| * Drop the task reference to the shared ancestor since |
| * current's path will hold a reference. (This also |
| * allows a put before the assignment.) |
| */ |
| put_seccomp_filter(thread); |
| smp_store_release(&thread->seccomp.filter, |
| caller->seccomp.filter); |
| |
| /* |
| * Don't let an unprivileged task work around |
| * the no_new_privs restriction by creating |
| * a thread that sets it up, enters seccomp, |
| * then dies. |
| */ |
| if (task_no_new_privs(caller)) |
| task_set_no_new_privs(thread); |
| |
| /* |
| * Opt the other thread into seccomp if needed. |
| * As threads are considered to be trust-realm |
| * equivalent (see ptrace_may_access), it is safe to |
| * allow one thread to transition the other. |
| */ |
| if (thread->seccomp.mode == SECCOMP_MODE_DISABLED) |
| seccomp_assign_mode(thread, SECCOMP_MODE_FILTER); |
| } |
| } |
| |
| /** |
| * seccomp_prepare_filter: Prepares a seccomp filter for use. |
| * @fprog: BPF program to install |
| * |
| * Returns filter on success or an ERR_PTR on failure. |
| */ |
| static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog) |
| { |
| struct seccomp_filter *sfilter; |
| int ret; |
| const bool save_orig = IS_ENABLED(CONFIG_CHECKPOINT_RESTORE); |
| |
| if (fprog->len == 0 || fprog->len > BPF_MAXINSNS) |
| return ERR_PTR(-EINVAL); |
| |
| BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter)); |
| |
| /* |
| * Installing a seccomp filter requires that the task has |
| * CAP_SYS_ADMIN in its namespace or be running with no_new_privs. |
| * This avoids scenarios where unprivileged tasks can affect the |
| * behavior of privileged children. |
| */ |
| if (!task_no_new_privs(current) && |
| security_capable_noaudit(current_cred(), current_user_ns(), |
| CAP_SYS_ADMIN) != 0) |
| return ERR_PTR(-EACCES); |
| |
| /* Allocate a new seccomp_filter */ |
| sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN); |
| if (!sfilter) |
| return ERR_PTR(-ENOMEM); |
| |
| ret = bpf_prog_create_from_user(&sfilter->prog, fprog, |
| seccomp_check_filter, save_orig); |
| if (ret < 0) { |
| kfree(sfilter); |
| return ERR_PTR(ret); |
| } |
| |
| atomic_set(&sfilter->usage, 1); |
| |
| return sfilter; |
| } |
| |
| /** |
| * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog |
| * @user_filter: pointer to the user data containing a sock_fprog. |
| * |
| * Returns 0 on success and non-zero otherwise. |
| */ |
| static struct seccomp_filter * |
| seccomp_prepare_user_filter(const char __user *user_filter) |
| { |
| struct sock_fprog fprog; |
| struct seccomp_filter *filter = ERR_PTR(-EFAULT); |
| |
| #ifdef CONFIG_COMPAT |
| if (in_compat_syscall()) { |
| struct compat_sock_fprog fprog32; |
| if (copy_from_user(&fprog32, user_filter, sizeof(fprog32))) |
| goto out; |
| fprog.len = fprog32.len; |
| fprog.filter = compat_ptr(fprog32.filter); |
| } else /* falls through to the if below. */ |
| #endif |
| if (copy_from_user(&fprog, user_filter, sizeof(fprog))) |
| goto out; |
| filter = seccomp_prepare_filter(&fprog); |
| out: |
| return filter; |
| } |
| |
| /** |
| * seccomp_attach_filter: validate and attach filter |
| * @flags: flags to change filter behavior |
| * @filter: seccomp filter to add to the current process |
| * |
| * Caller must be holding current->sighand->siglock lock. |
| * |
| * Returns 0 on success, -ve on error. |
| */ |
| static long seccomp_attach_filter(unsigned int flags, |
| struct seccomp_filter *filter) |
| { |
| unsigned long total_insns; |
| struct seccomp_filter *walker; |
| |
| assert_spin_locked(¤t->sighand->siglock); |
| |
| /* Validate resulting filter length. */ |
| total_insns = filter->prog->len; |
| for (walker = current->seccomp.filter; walker; walker = walker->prev) |
| total_insns += walker->prog->len + 4; /* 4 instr penalty */ |
| if (total_insns > MAX_INSNS_PER_PATH) |
| return -ENOMEM; |
| |
| /* If thread sync has been requested, check that it is possible. */ |
| if (flags & SECCOMP_FILTER_FLAG_TSYNC) { |
| int ret; |
| |
| ret = seccomp_can_sync_threads(); |
| if (ret) |
| return ret; |
| } |
| |
| /* |
| * If there is an existing filter, make it the prev and don't drop its |
| * task reference. |
| */ |
| filter->prev = current->seccomp.filter; |
| current->seccomp.filter = filter; |
| |
| /* Now that the new filter is in place, synchronize to all threads. */ |
| if (flags & SECCOMP_FILTER_FLAG_TSYNC) |
| seccomp_sync_threads(); |
| |
| return 0; |
| } |
| |
| /* get_seccomp_filter - increments the reference count of the filter on @tsk */ |
| void get_seccomp_filter(struct task_struct *tsk) |
| { |
| struct seccomp_filter *orig = tsk->seccomp.filter; |
| if (!orig) |
| return; |
| /* Reference count is bounded by the number of total processes. */ |
| atomic_inc(&orig->usage); |
| } |
| |
| static inline void seccomp_filter_free(struct seccomp_filter *filter) |
| { |
| if (filter) { |
| bpf_prog_destroy(filter->prog); |
| kfree(filter); |
| } |
| } |
| |
| /* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */ |
| void put_seccomp_filter(struct task_struct *tsk) |
| { |
| struct seccomp_filter *orig = tsk->seccomp.filter; |
| /* Clean up single-reference branches iteratively. */ |
| while (orig && atomic_dec_and_test(&orig->usage)) { |
| struct seccomp_filter *freeme = orig; |
| orig = orig->prev; |
| seccomp_filter_free(freeme); |
| } |
| } |
| |
| static void seccomp_init_siginfo(siginfo_t *info, int syscall, int reason) |
| { |
| memset(info, 0, sizeof(*info)); |
| info->si_signo = SIGSYS; |
| info->si_code = SYS_SECCOMP; |
| info->si_call_addr = (void __user *)KSTK_EIP(current); |
| info->si_errno = reason; |
| info->si_arch = syscall_get_arch(); |
| info->si_syscall = syscall; |
| } |
| |
| /** |
| * seccomp_send_sigsys - signals the task to allow in-process syscall emulation |
| * @syscall: syscall number to send to userland |
| * @reason: filter-supplied reason code to send to userland (via si_errno) |
| * |
| * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info. |
| */ |
| static void seccomp_send_sigsys(int syscall, int reason) |
| { |
| struct siginfo info; |
| seccomp_init_siginfo(&info, syscall, reason); |
| force_sig_info(SIGSYS, &info, current); |
| } |
| #endif /* CONFIG_SECCOMP_FILTER */ |
| |
| /* |
| * Secure computing mode 1 allows only read/write/exit/sigreturn. |
| * To be fully secure this must be combined with rlimit |
| * to limit the stack allocations too. |
| */ |
| static const int mode1_syscalls[] = { |
| __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn, |
| 0, /* null terminated */ |
| }; |
| |
| static void __secure_computing_strict(int this_syscall) |
| { |
| const int *syscall_whitelist = mode1_syscalls; |
| #ifdef CONFIG_COMPAT |
| if (in_compat_syscall()) |
| syscall_whitelist = get_compat_mode1_syscalls(); |
| #endif |
| do { |
| if (*syscall_whitelist == this_syscall) |
| return; |
| } while (*++syscall_whitelist); |
| |
| #ifdef SECCOMP_DEBUG |
| dump_stack(); |
| #endif |
| audit_seccomp(this_syscall, SIGKILL, SECCOMP_RET_KILL); |
| do_exit(SIGKILL); |
| } |
| |
| #ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER |
| void secure_computing_strict(int this_syscall) |
| { |
| int mode = current->seccomp.mode; |
| |
| if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) && |
| unlikely(current->ptrace & PT_SUSPEND_SECCOMP)) |
| return; |
| |
| if (mode == SECCOMP_MODE_DISABLED) |
| return; |
| else if (mode == SECCOMP_MODE_STRICT) |
| __secure_computing_strict(this_syscall); |
| else |
| BUG(); |
| } |
| #else |
| |
| #ifdef CONFIG_SECCOMP_FILTER |
| static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, |
| const bool recheck_after_trace) |
| { |
| u32 filter_ret, action; |
| int data; |
| |
| /* |
| * Make sure that any changes to mode from another thread have |
| * been seen after TIF_SECCOMP was seen. |
| */ |
| rmb(); |
| |
| filter_ret = seccomp_run_filters(sd); |
| data = filter_ret & SECCOMP_RET_DATA; |
| action = filter_ret & SECCOMP_RET_ACTION; |
| |
| switch (action) { |
| case SECCOMP_RET_ERRNO: |
| /* Set low-order bits as an errno, capped at MAX_ERRNO. */ |
| if (data > MAX_ERRNO) |
| data = MAX_ERRNO; |
| syscall_set_return_value(current, task_pt_regs(current), |
| -data, 0); |
| goto skip; |
| |
| case SECCOMP_RET_TRAP: |
| /* Show the handler the original registers. */ |
| syscall_rollback(current, task_pt_regs(current)); |
| /* Let the filter pass back 16 bits of data. */ |
| seccomp_send_sigsys(this_syscall, data); |
| goto skip; |
| |
| case SECCOMP_RET_TRACE: |
| /* We've been put in this state by the ptracer already. */ |
| if (recheck_after_trace) |
| return 0; |
| |
| /* ENOSYS these calls if there is no tracer attached. */ |
| if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) { |
| syscall_set_return_value(current, |
| task_pt_regs(current), |
| -ENOSYS, 0); |
| goto skip; |
| } |
| |
| /* Allow the BPF to provide the event message */ |
| ptrace_event(PTRACE_EVENT_SECCOMP, data); |
| /* |
| * The delivery of a fatal signal during event |
| * notification may silently skip tracer notification, |
| * which could leave us with a potentially unmodified |
| * syscall that the tracer would have liked to have |
| * changed. Since the process is about to die, we just |
| * force the syscall to be skipped and let the signal |
| * kill the process and correctly handle any tracer exit |
| * notifications. |
| */ |
| if (fatal_signal_pending(current)) |
| goto skip; |
| /* Check if the tracer forced the syscall to be skipped. */ |
| this_syscall = syscall_get_nr(current, task_pt_regs(current)); |
| if (this_syscall < 0) |
| goto skip; |
| |
| /* |
| * Recheck the syscall, since it may have changed. This |
| * intentionally uses a NULL struct seccomp_data to force |
| * a reload of all registers. This does not goto skip since |
| * a skip would have already been reported. |
| */ |
| if (__seccomp_filter(this_syscall, NULL, true)) |
| return -1; |
| |
| return 0; |
| |
| case SECCOMP_RET_ALLOW: |
| return 0; |
| |
| case SECCOMP_RET_KILL: |
| default: { |
| siginfo_t info; |
| audit_seccomp(this_syscall, SIGSYS, action); |
| /* Show the original registers in the dump. */ |
| syscall_rollback(current, task_pt_regs(current)); |
| /* Trigger a manual coredump since do_exit skips it. */ |
| seccomp_init_siginfo(&info, this_syscall, data); |
| do_coredump(&info); |
| do_exit(SIGSYS); |
| } |
| } |
| |
| unreachable(); |
| |
| skip: |
| audit_seccomp(this_syscall, 0, action); |
| return -1; |
| } |
| #else |
| static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, |
| const bool recheck_after_trace) |
| { |
| BUG(); |
| } |
| #endif |
| |
| int __secure_computing(const struct seccomp_data *sd) |
| { |
| int mode = current->seccomp.mode; |
| int this_syscall; |
| |
| if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) && |
| unlikely(current->ptrace & PT_SUSPEND_SECCOMP)) |
| return 0; |
| |
| this_syscall = sd ? sd->nr : |
| syscall_get_nr(current, task_pt_regs(current)); |
| |
| switch (mode) { |
| case SECCOMP_MODE_STRICT: |
| __secure_computing_strict(this_syscall); /* may call do_exit */ |
| return 0; |
| case SECCOMP_MODE_FILTER: |
| return __seccomp_filter(this_syscall, sd, false); |
| default: |
| BUG(); |
| } |
| } |
| #endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */ |
| |
| long prctl_get_seccomp(void) |
| { |
| return current->seccomp.mode; |
| } |
| |
| /** |
| * seccomp_set_mode_strict: internal function for setting strict seccomp |
| * |
| * Once current->seccomp.mode is non-zero, it may not be changed. |
| * |
| * Returns 0 on success or -EINVAL on failure. |
| */ |
| static long seccomp_set_mode_strict(void) |
| { |
| const unsigned long seccomp_mode = SECCOMP_MODE_STRICT; |
| long ret = -EINVAL; |
| |
| spin_lock_irq(¤t->sighand->siglock); |
| |
| if (!seccomp_may_assign_mode(seccomp_mode)) |
| goto out; |
| |
| #ifdef TIF_NOTSC |
| disable_TSC(); |
| #endif |
| seccomp_assign_mode(current, seccomp_mode); |
| ret = 0; |
| |
| out: |
| spin_unlock_irq(¤t->sighand->siglock); |
| |
| return ret; |
| } |
| |
| #ifdef CONFIG_SECCOMP_FILTER |
| /** |
| * seccomp_set_mode_filter: internal function for setting seccomp filter |
| * @flags: flags to change filter behavior |
| * @filter: struct sock_fprog containing filter |
| * |
| * This function may be called repeatedly to install additional filters. |
| * Every filter successfully installed will be evaluated (in reverse order) |
| * for each system call the task makes. |
| * |
| * Once current->seccomp.mode is non-zero, it may not be changed. |
| * |
| * Returns 0 on success or -EINVAL on failure. |
| */ |
| static long seccomp_set_mode_filter(unsigned int flags, |
| const char __user *filter) |
| { |
| const unsigned long seccomp_mode = SECCOMP_MODE_FILTER; |
| struct seccomp_filter *prepared = NULL; |
| long ret = -EINVAL; |
| |
| /* Validate flags. */ |
| if (flags & ~SECCOMP_FILTER_FLAG_MASK) |
| return -EINVAL; |
| |
| /* Prepare the new filter before holding any locks. */ |
| prepared = seccomp_prepare_user_filter(filter); |
| if (IS_ERR(prepared)) |
| return PTR_ERR(prepared); |
| |
| /* |
| * Make sure we cannot change seccomp or nnp state via TSYNC |
| * while another thread is in the middle of calling exec. |
| */ |
| if (flags & SECCOMP_FILTER_FLAG_TSYNC && |
| mutex_lock_killable(¤t->signal->cred_guard_mutex)) |
| goto out_free; |
| |
| spin_lock_irq(¤t->sighand->siglock); |
| |
| if (!seccomp_may_assign_mode(seccomp_mode)) |
| goto out; |
| |
| ret = seccomp_attach_filter(flags, prepared); |
| if (ret) |
| goto out; |
| /* Do not free the successfully attached filter. */ |
| prepared = NULL; |
| |
| seccomp_assign_mode(current, seccomp_mode); |
| out: |
| spin_unlock_irq(¤t->sighand->siglock); |
| if (flags & SECCOMP_FILTER_FLAG_TSYNC) |
| mutex_unlock(¤t->signal->cred_guard_mutex); |
| out_free: |
| seccomp_filter_free(prepared); |
| return ret; |
| } |
| #else |
| static inline long seccomp_set_mode_filter(unsigned int flags, |
| const char __user *filter) |
| { |
| return -EINVAL; |
| } |
| #endif |
| |
| /* Common entry point for both prctl and syscall. */ |
| static long do_seccomp(unsigned int op, unsigned int flags, |
| const char __user *uargs) |
| { |
| switch (op) { |
| case SECCOMP_SET_MODE_STRICT: |
| if (flags != 0 || uargs != NULL) |
| return -EINVAL; |
| return seccomp_set_mode_strict(); |
| case SECCOMP_SET_MODE_FILTER: |
| return seccomp_set_mode_filter(flags, uargs); |
| default: |
| return -EINVAL; |
| } |
| } |
| |
| SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags, |
| const char __user *, uargs) |
| { |
| return do_seccomp(op, flags, uargs); |
| } |
| |
| /** |
| * prctl_set_seccomp: configures current->seccomp.mode |
| * @seccomp_mode: requested mode to use |
| * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER |
| * |
| * Returns 0 on success or -EINVAL on failure. |
| */ |
| long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter) |
| { |
| unsigned int op; |
| char __user *uargs; |
| |
| switch (seccomp_mode) { |
| case SECCOMP_MODE_STRICT: |
| op = SECCOMP_SET_MODE_STRICT; |
| /* |
| * Setting strict mode through prctl always ignored filter, |
| * so make sure it is always NULL here to pass the internal |
| * check in do_seccomp(). |
| */ |
| uargs = NULL; |
| break; |
| case SECCOMP_MODE_FILTER: |
| op = SECCOMP_SET_MODE_FILTER; |
| uargs = filter; |
| break; |
| default: |
| return -EINVAL; |
| } |
| |
| /* prctl interface doesn't have flags, so they are always zero. */ |
| return do_seccomp(op, 0, uargs); |
| } |
| |
| #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE) |
| long seccomp_get_filter(struct task_struct *task, unsigned long filter_off, |
| void __user *data) |
| { |
| struct seccomp_filter *filter; |
| struct sock_fprog_kern *fprog; |
| long ret; |
| unsigned long count = 0; |
| |
| if (!capable(CAP_SYS_ADMIN) || |
| current->seccomp.mode != SECCOMP_MODE_DISABLED) { |
| return -EACCES; |
| } |
| |
| spin_lock_irq(&task->sighand->siglock); |
| if (task->seccomp.mode != SECCOMP_MODE_FILTER) { |
| ret = -EINVAL; |
| goto out; |
| } |
| |
| filter = task->seccomp.filter; |
| while (filter) { |
| filter = filter->prev; |
| count++; |
| } |
| |
| if (filter_off >= count) { |
| ret = -ENOENT; |
| goto out; |
| } |
| count -= filter_off; |
| |
| filter = task->seccomp.filter; |
| while (filter && count > 1) { |
| filter = filter->prev; |
| count--; |
| } |
| |
| if (WARN_ON(count != 1 || !filter)) { |
| /* The filter tree shouldn't shrink while we're using it. */ |
| ret = -ENOENT; |
| goto out; |
| } |
| |
| fprog = filter->prog->orig_prog; |
| if (!fprog) { |
| /* This must be a new non-cBPF filter, since we save |
| * every cBPF filter's orig_prog above when |
| * CONFIG_CHECKPOINT_RESTORE is enabled. |
| */ |
| ret = -EMEDIUMTYPE; |
| goto out; |
| } |
| |
| ret = fprog->len; |
| if (!data) |
| goto out; |
| |
| get_seccomp_filter(task); |
| spin_unlock_irq(&task->sighand->siglock); |
| |
| if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog))) |
| ret = -EFAULT; |
| |
| put_seccomp_filter(task); |
| return ret; |
| |
| out: |
| spin_unlock_irq(&task->sighand->siglock); |
| return ret; |
| } |
| #endif |