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| author | Daniel Borkmann <daniel@iogearbox.net> | 2019-03-01 22:05:29 +0100 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2019-03-01 21:24:08 -0800 |
| commit | 3612af783cf52c74a031a2f11b82247b2599d3cd (patch) | |
| tree | 85a1b50626d47bd26b022cff8e9efc426c6b82ac /kernel/bpf/verifier.c | |
| parent | d1a2930d8a992fb6ac2529449f81a0056e1b98d1 (diff) | |
| download | lwn-3612af783cf52c74a031a2f11b82247b2599d3cd.tar.gz lwn-3612af783cf52c74a031a2f11b82247b2599d3cd.zip | |
bpf: fix sanitation rewrite in case of non-pointers
Marek reported that he saw an issue with the below snippet in that
timing measurements where off when loaded as unpriv while results
were reasonable when loaded as privileged:
[...]
uint64_t a = bpf_ktime_get_ns();
uint64_t b = bpf_ktime_get_ns();
uint64_t delta = b - a;
if ((int64_t)delta > 0) {
[...]
Turns out there is a bug where a corner case is missing in the fix
d3bd7413e0ca ("bpf: fix sanitation of alu op with pointer / scalar
type from different paths"), namely fixup_bpf_calls() only checks
whether aux has a non-zero alu_state, but it also needs to test for
the case of BPF_ALU_NON_POINTER since in both occasions we need to
skip the masking rewrite (as there is nothing to mask).
Fixes: d3bd7413e0ca ("bpf: fix sanitation of alu op with pointer / scalar type from different paths")
Reported-by: Marek Majkowski <marek@cloudflare.com>
Reported-by: Arthur Fabre <afabre@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/netdev/CAJPywTJqP34cK20iLM5YmUMz9KXQOdu1-+BZrGMAGgLuBWz7fg@mail.gmail.com/T/
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf/verifier.c')
| -rw-r--r-- | kernel/bpf/verifier.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8f295b790297..5fcce2f4209d 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -6920,7 +6920,8 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env) u32 off_reg; aux = &env->insn_aux_data[i + delta]; - if (!aux->alu_state) + if (!aux->alu_state || + aux->alu_state == BPF_ALU_NON_POINTER) continue; isneg = aux->alu_state & BPF_ALU_NEG_VALUE; |