diff options
| author | Alex Gartrell <agartrell@fb.com> | 2015-07-23 21:24:40 (GMT) |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-07-27 07:54:10 (GMT) |
| commit | 24b4d2abd0bd628f396dada3e915d395cbf459eb (patch) | |
| tree | ff4993b4c6f7c86b2f325d93d5c944446e5d5c61 /kernel/bpf | |
| parent | 6ecfdd28c8a6504349ca8501316b1ed3f639ce44 (diff) | |
| download | linux-24b4d2abd0bd628f396dada3e915d395cbf459eb.tar.xz | |
ebpf: Allow dereferences of PTR_TO_STACK registers
mov %rsp, %r1 ; r1 = rsp
add $-8, %r1 ; r1 = rsp - 8
store_q $123, -8(%rsp) ; *(u64*)r1 = 123 <- valid
store_q $123, (%r1) ; *(u64*)r1 = 123 <- previously invalid
mov $0, %r0
exit ; Always need to exit
And we'd get the following error:
0: (bf) r1 = r10
1: (07) r1 += -8
2: (7a) *(u64 *)(r10 -8) = 999
3: (7a) *(u64 *)(r1 +0) = 999
R1 invalid mem access 'fp'
Unable to load program
We already know that a register is a stack address and the appropriate
offset, so we should be able to validate those references as well.
Signed-off-by: Alex Gartrell <agartrell@fb.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/verifier.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 039d866..cd307df 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -648,6 +648,9 @@ static int check_mem_access(struct verifier_env *env, u32 regno, int off, 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; @@ -667,7 +670,8 @@ static int check_mem_access(struct verifier_env *env, u32 regno, int off, if (!err && t == BPF_READ && value_regno >= 0) mark_reg_unknown_value(state->regs, value_regno); - } else if (state->regs[regno].type == FRAME_PTR) { + } 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; |