diff mbox series

[94/97] slirp: ip_reass: Fix use after free

Message ID 20191001234616.7825-95-mdroth@linux.vnet.ibm.com (mailing list archive)
State New, archived
Headers show
Series Patch Round-up for stable 4.0.1, freeze on 2019-10-10 | expand

Commit Message

Michael Roth Oct. 1, 2019, 11:46 p.m. UTC 
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>
---
 slirp/src/ip_input.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/slirp/src/ip_input.c b/slirp/src/ip_input.c
index 68a99de5b5..89ae04e0c1 100644
--- a/slirp/src/ip_input.c
+++ b/slirp/src/ip_input.c
@@ -297,6 +297,7 @@  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;
@@ -304,9 +305,10 @@  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));
 	}
 
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