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authorDaniel Borkmann <daniel@iogearbox.net>2019-03-01 22:05:29 +0100
committerAlexei Starovoitov <ast@kernel.org>2019-03-01 21:24:08 -0800
commit3612af783cf52c74a031a2f11b82247b2599d3cd (patch)
tree85a1b50626d47bd26b022cff8e9efc426c6b82ac /kernel
parentd1a2930d8a992fb6ac2529449f81a0056e1b98d1 (diff)
downloadlinux-3612af783cf52c74a031a2f11b82247b2599d3cd.tar.bz2
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')
-rw-r--r--kernel/bpf/verifier.c3
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;