diff options
| author | Alexei Starovoitov <ast@fb.com> | 2017-03-24 15:57:33 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-03-24 20:51:28 -0700 |
| commit | b1977682a3858b5584ffea7cfb7bd863f68db18d (patch) | |
| tree | f255d32b2a4e2b72811b36bbd04b27ef9fd2a947 /kernel | |
| parent | 43a6684519ab0a6c52024b5e25322476cabad893 (diff) | |
bpf: improve verifier packet range checks
llvm can optimize the 'if (ptr > data_end)' checks to be in the order
slightly different than the original C code which will confuse verifier.
Like:
if (ptr + 16 > data_end)
return TC_ACT_SHOT;
// may be followed by
if (ptr + 14 > data_end)
return TC_ACT_SHOT;
while llvm can see that 'ptr' is valid for all 16 bytes,
the verifier could not.
Fix verifier logic to account for such case and add a test.
Reported-by: Huapeng Zhou <hzhou@fb.com>
Fixes: 969bf05eb3ce ("bpf: direct packet access")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/verifier.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 796b68d00119..5e6202e62265 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1973,14 +1973,15 @@ static void find_good_pkt_pointers(struct bpf_verifier_state *state, for (i = 0; i < MAX_BPF_REG; i++) if (regs[i].type == PTR_TO_PACKET && regs[i].id == dst_reg->id) - regs[i].range = dst_reg->off; + /* keep the maximum range already checked */ + regs[i].range = max(regs[i].range, dst_reg->off); for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { if (state->stack_slot_type[i] != STACK_SPILL) continue; reg = &state->spilled_regs[i / BPF_REG_SIZE]; if (reg->type == PTR_TO_PACKET && reg->id == dst_reg->id) - reg->range = dst_reg->off; + reg->range = max(reg->range, dst_reg->off); } } |