diff options
| author | Ben Hutchings <ben@decadent.org.uk> | 2017-12-23 02:26:17 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-12-29 17:43:00 +0100 |
| commit | 37435f7e80ef9adc32a69013c18f135e3f434244 (patch) | |
| tree | a67c019c8f446ac26ddd81ee14a45a7c1201247a | |
| parent | 69cf72b2879167364d2a97211fbb26ca0e374bcf (diff) | |
bpf/verifier: Fix states_equal() comparison of pointer and UNKNOWN
An UNKNOWN_VALUE is not supposed to be derived from a pointer, unless
pointer leaks are allowed. Therefore, states_equal() must not treat
a state with a pointer in a register as "equal" to a state with an
UNKNOWN_VALUE in that register.
This was fixed differently upstream, but the code around here was
largely rewritten in 4.14 by commit f1174f77b50c "bpf/verifier: rework
value tracking". The bug can be detected by the bpf/verifier sub-test
"pointer/scalar confusion in state equality check (way 1)".
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Edward Cree <ecree@solarflare.com>
Cc: Jann Horn <jannh@google.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
| -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 8b1ebe4c6aba..d7eeebfafe8d 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2722,11 +2722,12 @@ static bool states_equal(struct bpf_verifier_env *env, /* If we didn't map access then again we don't care about the * mismatched range values and it's ok if our old type was - * UNKNOWN and we didn't go to a NOT_INIT'ed reg. + * UNKNOWN and we didn't go to a NOT_INIT'ed or pointer reg. */ if (rold->type == NOT_INIT || (!varlen_map_access && rold->type == UNKNOWN_VALUE && - rcur->type != NOT_INIT)) + rcur->type != NOT_INIT && + !__is_pointer_value(env->allow_ptr_leaks, rcur))) continue; /* Don't care about the reg->id in this case. */ |