slrip: ip_reass: Fix use after free
Using ip_deq after m_free might read pointers from an allocation reuse.
This would be difficult to exploit, but that is still related with
CVE-2019-14378 which generates fragmented IP packets that would trigger this
issue and at least produce a DoS.
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
(from libslirp.git commit c59279437eda91841b9d26079c70b8a540d41204)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
diff --git a/slirp/ip_input.c b/slirp/ip_input.c
index 6e291ea..01b3f9d 100644
--- a/slirp/ip_input.c
+++ b/slirp/ip_input.c
@@ -300,6 +300,7 @@
*/
while (q != (struct ipasfrag*)&fp->frag_link &&
ip->ip_off + ip->ip_len > q->ipf_off) {
+ struct ipasfrag *prev;
i = (ip->ip_off + ip->ip_len) - q->ipf_off;
if (i < q->ipf_len) {
q->ipf_len -= i;
@@ -307,9 +308,10 @@
m_adj(dtom(slirp, q), i);
break;
}
+ prev = q;
q = q->ipf_next;
- m_free(dtom(slirp, q->ipf_prev));
- ip_deq(q->ipf_prev);
+ ip_deq(prev);
+ m_free(dtom(slirp, prev));
}
insert:
