From e2d2afe15ed452f91797a80dbc0a17838ba03ed4 Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Tue, 29 Nov 2016 12:27:09 -0500 Subject: [PATCH] bpf: fix states equal logic for varlen access If we have a branch that looks something like this int foo = map->value; if (condition) { foo += blah; } else { foo = bar; } map->array[foo] = baz; We will incorrectly assume that the !condition branch is equal to the condition branch as the register for foo will be UNKNOWN_VALUE in both cases. We need to adjust this logic to only do this if we didn't do a varlen access after we processed the !condition branch, otherwise we have different ranges and need to check the other branch as well. Fixes: 484611357c19 ("bpf: allow access into map value arrays") Reported-by: Jann Horn Signed-off-by: Josef Bacik Acked-by: Alexei Starovoitov Acked-by: Daniel Borkmann Signed-off-by: David S. Miller --- kernel/bpf/verifier.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 6a936159c6e0..8199821f54cf 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2454,6 +2454,7 @@ static bool states_equal(struct bpf_verifier_env *env, struct bpf_verifier_state *old, struct bpf_verifier_state *cur) { + bool varlen_map_access = env->varlen_map_value_access; struct bpf_reg_state *rold, *rcur; int i; @@ -2467,12 +2468,17 @@ static bool states_equal(struct bpf_verifier_env *env, /* If the ranges were not the same, but everything else was and * we didn't do a variable access into a map then we are a-ok. */ - if (!env->varlen_map_value_access && + if (!varlen_map_access && rold->type == rcur->type && rold->imm == rcur->imm) continue; + /* 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. + */ if (rold->type == NOT_INIT || - (rold->type == UNKNOWN_VALUE && rcur->type != NOT_INIT)) + (!varlen_map_access && rold->type == UNKNOWN_VALUE && + rcur->type != NOT_INIT)) continue; if (rold->type == PTR_TO_PACKET && rcur->type == PTR_TO_PACKET && -- 2.30.2