On 11/28/2016 10:04 PM, Alexei Starovoitov wrote:
On Mon, Nov 28, 2016 at 02:44:10PM -0500, Josef Bacik wrote:
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.
Signed-off-by: Josef Bacik <jba...@fb.com>
---
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 89f787c..2c8a688 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2478,6 +2478,7 @@ static bool states_equal(struct bpf_verifier_env *env,
{
struct bpf_reg_state *rold, *rcur;
int i;
+ bool map_access = env->varlen_map_value_access;
that's a bit misleading name for the variable.
Pls call it varlen_map_access.
for (i = 0; i < MAX_BPF_REG; i++) {
rold = &old->regs[i];
@@ -2489,12 +2490,17 @@ 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 (!map_access &&
rold->type == rcur->type && rold->imm == rcur->imm)
just noticed that this one is missing comparing rold->id == rcur->id
Do you want me to fix that here? I'll fix up the rest of the stuff, and Daniels
things as well. Thanks,
Josef
