diff options
| author | Daniel Borkmann <dborkman@redhat.com> | 2014-04-05 01:04:03 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-04-07 12:54:39 -0400 |
| commit | 5f9fde5f799df7156eeb3fa58282e9fd2f38a5f8 (patch) | |
| tree | 26556f3c6534b9f725615d7db4a3772338add528 /net/core | |
| parent | d80e773f16f66a610e04f6875d4da84e74a8fb6c (diff) | |
| download | linux-5f9fde5f799df7156eeb3fa58282e9fd2f38a5f8.tar.gz | |
net: filter: be more defensive on div/mod by X==0
The old interpreter behaviour was that we returned with 0 whenever we found a division by 0 would take place. In the new interpreter we would currently just skip that instead and continue execution. It's true that a value of 0 as return might not be appropriate in all cases, but current users (socket filters -> drop packet, seccomp -> SECCOMP_RET_KILL, cls_bpf -> unclassified, etc) seem fine with that behaviour. Better this than undefined BPF program behaviour as it's expected that A contains the result of the division. In future, as more use cases open up, we could further adapt this return value to our needs, if necessary. So reintroduce return of 0 for division by 0 as in the old interpreter. Also in case of K which is guaranteed to be 32bit wide, sk_chk_filter() already takes care of preventing division by 0 invoked through K, so we can generally spare us these tests. Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Reviewed-by: Alexei Starovoitov <ast@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/filter.c | 32 |
1 files changed, 16 insertions, 16 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index 765556ba32ef..e08b3822c72a 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -295,43 +295,43 @@ select_insn: (*(s64 *) &A) >>= K; CONT; BPF_ALU64_BPF_MOD_BPF_X: + if (unlikely(X == 0)) + return 0; tmp = A; - if (X) - A = do_div(tmp, X); + A = do_div(tmp, X); CONT; BPF_ALU_BPF_MOD_BPF_X: + if (unlikely(X == 0)) + return 0; tmp = (u32) A; - if (X) - A = do_div(tmp, (u32) X); + A = do_div(tmp, (u32) X); CONT; BPF_ALU64_BPF_MOD_BPF_K: tmp = A; - if (K) - A = do_div(tmp, K); + A = do_div(tmp, K); CONT; BPF_ALU_BPF_MOD_BPF_K: tmp = (u32) A; - if (K) - A = do_div(tmp, (u32) K); + A = do_div(tmp, (u32) K); CONT; BPF_ALU64_BPF_DIV_BPF_X: - if (X) - do_div(A, X); + if (unlikely(X == 0)) + return 0; + do_div(A, X); CONT; BPF_ALU_BPF_DIV_BPF_X: + if (unlikely(X == 0)) + return 0; tmp = (u32) A; - if (X) - do_div(tmp, (u32) X); + do_div(tmp, (u32) X); A = (u32) tmp; CONT; BPF_ALU64_BPF_DIV_BPF_K: - if (K) - do_div(A, K); + do_div(A, K); CONT; BPF_ALU_BPF_DIV_BPF_K: tmp = (u32) A; - if (K) - do_div(tmp, (u32) K); + do_div(tmp, (u32) K); A = (u32) tmp; CONT; BPF_ALU_BPF_END_BPF_TO_BE: |