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From a33ea192428d9c9307f1140f3e25631a6ef7657c Mon Sep 17 00:00:00 2001
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From: Jon Maloy <jmaloy@redhat.com>
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Date: Sat, 20 Jun 2020 15:02:59 -0400
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Subject: [PATCH 12/12] Fix use-afte-free in ip_reass() (CVE-2020-1983)
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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: Jon Maloy <jmaloy@redhat.com>
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Message-id: <20200620150259.3352467-2-jmaloy@redhat.com>
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Patchwork-id: 97678
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O-Subject: [RHEL-8.3.0 qemu-kvm PATCH 1/1] Fix use-afte-free in ip_reass() (CVE-2020-1983)
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Bugzilla: 1838070
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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From: Marc-André Lureau <marcandre.lureau@redhat.com>
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The q pointer is updated when the mbuf data is moved from m_dat to
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m_ext.
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m_ext buffer may also be realloc()'ed and moved during m_cat():
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q should also be updated in this case.
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Reported-by: Aviv Sasson <asasson@paloaltonetworks.com>
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Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
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Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
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(cherry picked from libslirp commit 9bd6c5913271eabcb7768a58197ed3301fe19f2d)
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Signed-off-by: Jon Maloy <jmaloy@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 | 5 ++---
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1 file changed, 2 insertions(+), 3 deletions(-)
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diff --git a/slirp/src/ip_input.c b/slirp/src/ip_input.c
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index df1c846ade..0f5d522ec1 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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@@ -329,7 +329,7 @@ insert:
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q = fp->frag_link.next;
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m = dtom(slirp, q);
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- int was_ext = m->m_flags & M_EXT;
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+ int delta = (char *)q - (m->m_flags & M_EXT ? m->m_ext : m->m_dat);
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q = (struct ipasfrag *)q->ipf_next;
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while (q != (struct ipasfrag *)&fp->frag_link) {
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@@ -353,8 +353,7 @@ insert:
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* the old buffer (in the mbuf), so we must point ip
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* into the new buffer.
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*/
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- if (!was_ext && m->m_flags & M_EXT) {
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- int delta = (char *)q - m->m_dat;
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+ if (m->m_flags & M_EXT) {
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q = (struct ipasfrag *)(m->m_ext + delta);
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}
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--
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2.27.0
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