From c59279437eda91841b9d26079c70b8a540d41204 Mon Sep 17 00:00:00 2001
From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date: Mon, 26 Aug 2019 00:55:03 +0200
Subject: [PATCH] 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>
---
Taken from https://gitlab.freedesktop.org/slirp/libslirp/commit/c5927943
slirp/src/ip_input.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/slirp/src/ip_input.c b/slirp/src/ip_input.c
index 7364ce0..aa514ae 100644
--- a/slirp/src/ip_input.c
+++ b/slirp/src/ip_input.c
@@ -292,6 +292,7 @@ static struct ip *ip_reass(Slirp *slirp, struct ip *ip, struct ipq *fp)
*/
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;
@@ -299,9 +300,10 @@ static struct ip *ip_reass(Slirp *slirp, struct ip *ip, struct ipq *fp)
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:
--
2.22.0