From a4c22009a465ebe5fd0c09699e61ad0423b8849d Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= <philmd@redhat.com>

Date: Fri, 6 Sep 2019 14:00:34 +0100

Subject: [PATCH 07/22] Using ip_deq after m_free might read pointers from an

 allocation reuse.

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RH-Author: Philippe Mathieu-Daudé <philmd@redhat.com>

Message-id: <20190906140034.19722-2-philmd@redhat.com>

Patchwork-id: 90306

O-Subject: [RHEL-7.7 qemu-kvm-ma + RHEL-7.7 qemu-kvm-rhev + RHEL-8.1.0 qemu-kvm PATCH 1/1] Using ip_deq after m_free might read pointers from an allocation reuse.

Bugzilla: 1749724

RH-Acked-by: Thomas Huth <thuth@redhat.com>

RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>

RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

From: Samuel Thibault <samuel.thibault@ens-lyon.org>

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>

(cherry picked from libslirp commit c59279437eda91841b9d26079c70b8a540d41204)

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>

---

 slirp/ip_input.c | 6 ++++--

 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/slirp/ip_input.c b/slirp/ip_input.c

index 07d8808..7cf0133 100644

--- a/slirp/ip_input.c

+++ b/slirp/ip_input.c

@@ -300,6 +300,7 @@ 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;

@@ -307,9 +308,10 @@ 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));

 	}

 insert:

-- 

1.8.3.1