Re: ney/key: slab-out-of-bounds in parse_ipsecrequests

[Cong Wang]

On Wed, Apr 12, 2017 at 8:02 AM, Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
> Hi,
>
> I've got the following error report while fuzzing the kernel with syzkaller.
>
> On commit 39da7c509acff13fc8cb12ec1bb20337c988ed36 (4.11-rc6).
>
> A reproducer and .config are attached.
>
> When subtracting rq->sadb_x_ipsecrequest_len from len it can become
> negative and the while loop condition remains true.

Good catch! Seems the fix is pretty straight forward:

diff --git a/net/key/af_key.c b/net/key/af_key.c
index c6252ed..cbce595 100644
--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -1945,7 +1945,7 @@ parse_ipsecrequests(struct xfrm_policy *xp,
struct sadb_x_policy *pol)
        if (pol->sadb_x_policy_len * 8 < sizeof(struct sadb_x_policy))
                return -EINVAL;

-       while (len >= sizeof(struct sadb_x_ipsecrequest)) {
+       while (len >= (int)sizeof(struct sadb_x_ipsecrequest)) {
                if ((err = parse_ipsecrequest(xp, rq)) < 0)
                        return err;
                len -= rq->sadb_x_ipsecrequest_len;

But pol->sadb_x_policy_len and rq->sadb_x_ipsecrequest_len
are controllable by user (fortunately root), I am feeling there might
be other problem I miss too.