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authorJosef Bacik <jbacik@fb.com>2016-11-29 12:27:09 -0500
committerDavid S. Miller <davem@davemloft.net>2016-11-30 14:50:52 -0500
commite2d2afe15ed452f91797a80dbc0a17838ba03ed4 (patch)
tree44cb85851f4f9aebe00a6405197e4766bed2cf83 /kernel
parent0fcba2894c6b370ebf4b49099d20ff6333a430f7 (diff)
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 <jannh@google.com> Signed-off-by: Josef Bacik <jbacik@fb.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/verifier.c10
1 files 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 &&