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From c59279437eda91841b9d26079c70b8a540d41204 Mon Sep 17 00:00:00 2001
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From: Samuel Thibault <samuel.thibault@ens-lyon.org>
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Date: Mon, 26 Aug 2019 00:55:03 +0200
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Subject: [PATCH] ip_reass: Fix use after free
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Using ip_deq after m_free might read pointers from an allocation reuse.
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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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---
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src/ip_input.c | 6 ++++--
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1 file changed, 4 insertions(+), 2 deletions(-)
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diff -up slirp4netns-4992082b2af77c09bca6bd8504e2ebfa5e118c18/qemu/slirp/src/ip_input.c.CVE-2019-15890 slirp4netns-4992082b2af77c09bca6bd8504e2ebfa5e118c18/qemu/slirp/src/ip_input.c
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--- slirp4netns-4992082b2af77c09bca6bd8504e2ebfa5e118c18/qemu/slirp/src/ip_input.c.CVE-2019-15890 2020-02-26 14:58:52.081548244 +0100
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+++ slirp4netns-4992082b2af77c09bca6bd8504e2ebfa5e118c18/qemu/slirp/src/ip_input.c 2020-02-26 15:00:48.144123448 +0100
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@@ -297,6 +297,7 @@ ip_reass(Slirp *slirp, struct ip *ip, st
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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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@@ -304,9 +305,10 @@ ip_reass(Slirp *slirp, struct ip *ip, st
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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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insert:
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