diff options
| author | Daniel Borkmann <daniel@iogearbox.net> | 2021-02-05 17:20:14 +0100 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2021-02-10 01:31:45 +0100 |
| commit | ee114dd64c0071500345439fc79dd5e0f9d106ed (patch) | |
| tree | 32a6a5f19f508c60da0e9eaef0d419c26bdf2063 /kernel/bpf | |
| parent | 6183f4d3a0a2ad230511987c6c362ca43ec0055f (diff) | |
bpf: Fix verifier jsgt branch analysis on max bound
Fix incorrect is_branch{32,64}_taken() analysis for the jsgt case. The return
code for both will tell the caller whether a given conditional jump is taken
or not, e.g. 1 means branch will be taken [for the involved registers] and the
goto target will be executed, 0 means branch will not be taken and instead we
fall-through to the next insn, and last but not least a -1 denotes that it is
not known at verification time whether a branch will be taken or not. Now while
the jsgt has the branch-taken case correct with reg->s32_min_value > sval, the
branch-not-taken case is off-by-one when testing for reg->s32_max_value < sval
since the branch will also be taken for reg->s32_max_value == sval. The jgt
branch analysis, for example, gets this right.
Fixes: 3f50f132d840 ("bpf: Verifier, do explicit ALU32 bounds tracking")
Fixes: 4f7b3e82589e ("bpf: improve verifier branch analysis")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/verifier.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index e7368c5eacb7..67ea0ac3333c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -6877,7 +6877,7 @@ static int is_branch32_taken(struct bpf_reg_state *reg, u32 val, u8 opcode) case BPF_JSGT: if (reg->s32_min_value > sval) return 1; - else if (reg->s32_max_value < sval) + else if (reg->s32_max_value <= sval) return 0; break; case BPF_JLT: @@ -6950,7 +6950,7 @@ static int is_branch64_taken(struct bpf_reg_state *reg, u64 val, u8 opcode) case BPF_JSGT: if (reg->smin_value > sval) return 1; - else if (reg->smax_value < sval) + else if (reg->smax_value <= sval) return 0; break; case BPF_JLT: |