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
> 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))
> + (!map_access && (rold->type == UNKNOWN_VALUE &&
> + rcur->type != NOT_INIT)))
please drop unnecessary ( )
