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From ab9ebc29bb9bb142e73a160750a451d40bfe9746 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= <philmd@redhat.com>
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Date: Mon, 16 Sep 2019 17:07:00 +0100
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Subject: Using ip_deq after m_free might read pointers from an allocation
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reuse.
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Philippe Mathieu-Daudé <philmd@redhat.com>
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Message-id: <20190916170700.647-2-philmd@redhat.com>
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Patchwork-id: 90470
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O-Subject: [RHEL-AV-8.1.0 qemu-kvm PATCH 1/1] Using ip_deq after m_free might read pointers from an allocation reuse.
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Bugzilla: 1749737
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RH-Acked-by: Danilo de Paula <ddepaula@redhat.com>
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RH-Acked-by: John Snow <jsnow@redhat.com>
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From: Samuel Thibault <samuel.thibault@ens-lyon.org>
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This would be difficult to exploit, but that is still related with
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CVE-2019-14378 which generates fragmented IP packets that would trigger this
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issue and at least produce a DoS.
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Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
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(cherry picked from libslirp commit c59279437eda91841b9d26079c70b8a540d41204)
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Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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slirp/src/ip_input.c | 7 +++++--
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1 file changed, 5 insertions(+), 2 deletions(-)
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diff --git a/slirp/src/ip_input.c b/slirp/src/ip_input.c
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index 8c75d91495..df1c846ade 100644
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--- a/slirp/src/ip_input.c
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+++ b/slirp/src/ip_input.c
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@@ -292,6 +292,7 @@ static struct ip *ip_reass(Slirp *slirp, struct ip *ip, struct ipq *fp)
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*/
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while (q != (struct ipasfrag *)&fp->frag_link &&
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ip->ip_off + ip->ip_len > q->ipf_off) {
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+ struct ipasfrag *prev;
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i = (ip->ip_off + ip->ip_len) - q->ipf_off;
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if (i < q->ipf_len) {
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q->ipf_len -= i;
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@@ -299,9 +300,11 @@ static struct ip *ip_reass(Slirp *slirp, struct ip *ip, struct ipq *fp)
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m_adj(dtom(slirp, q), i);
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break;
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}
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+ prev = q;
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q = q->ipf_next;
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- m_free(dtom(slirp, q->ipf_prev));
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- ip_deq(q->ipf_prev);
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+ ip_deq(prev);
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+ m_free(dtom(slirp, prev));
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+
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}
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insert:
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--
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2.21.0
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