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>
/* 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. */