bpf: fix matching of data/data_end in verifier
The ctx structure passed into bpf programs is different depending on bpf
program type. The verifier incorrectly marked ctx->data and ctx->data_end
access based on ctx offset only. That caused loads in tracing programs
int bpf_prog(struct pt_regs *ctx) { .. ctx->ax .. }
to be incorrectly marked as PTR_TO_PACKET which later caused verifier
to reject the program that was actually valid in tracing context.
Fix this by doing program type specific matching of ctx offsets.
Fixes: 969bf05eb3ce ("bpf: direct packet access")
Reported-by: Sasha Goldshtein <goldshtn@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 668e079..eec9f90 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -126,31 +126,6 @@
* 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 */
-
- /* PTR_TO_PACKET represents:
- * skb->data
- * skb->data + imm
- * skb->data + (u16) var
- * skb->data + (u16) var + imm
- * if (range > 0) then [ptr, ptr + range - off) is safe to access
- * if (id > 0) means that some 'var' was added
- * if (off > 0) menas that 'imm' was added
- */
- PTR_TO_PACKET,
- PTR_TO_PACKET_END, /* skb->data + headlen */
-};
-
struct reg_state {
enum bpf_reg_type type;
union {
@@ -695,10 +670,10 @@
/* 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)
+ enum bpf_access_type t, enum bpf_reg_type *reg_type)
{
if (env->prog->aux->ops->is_valid_access &&
- env->prog->aux->ops->is_valid_access(off, size, t)) {
+ env->prog->aux->ops->is_valid_access(off, size, t, reg_type)) {
/* 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;
@@ -798,21 +773,19 @@
mark_reg_unknown_value(state->regs, value_regno);
} else if (reg->type == PTR_TO_CTX) {
+ enum bpf_reg_type reg_type = UNKNOWN_VALUE;
+
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);
+ err = check_ctx_access(env, off, size, t, ®_type);
if (!err && t == BPF_READ && value_regno >= 0) {
mark_reg_unknown_value(state->regs, value_regno);
- if (off == offsetof(struct __sk_buff, data) &&
- env->allow_ptr_leaks)
+ if (env->allow_ptr_leaks)
/* note that reg.[id|off|range] == 0 */
- state->regs[value_regno].type = PTR_TO_PACKET;
- else if (off == offsetof(struct __sk_buff, data_end) &&
- env->allow_ptr_leaks)
- state->regs[value_regno].type = PTR_TO_PACKET_END;
+ state->regs[value_regno].type = reg_type;
}
} else if (reg->type == FRAME_PTR || reg->type == PTR_TO_STACK) {