From a33ea192428d9c9307f1140f3e25631a6ef7657c Mon Sep 17 00:00:00 2001 From: Jon Maloy Date: Sat, 20 Jun 2020 15:02:59 -0400 Subject: [PATCH 12/12] Fix use-afte-free in ip_reass() (CVE-2020-1983) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Jon Maloy Message-id: <20200620150259.3352467-2-jmaloy@redhat.com> Patchwork-id: 97678 O-Subject: [RHEL-8.3.0 qemu-kvm PATCH 1/1] Fix use-afte-free in ip_reass() (CVE-2020-1983) Bugzilla: 1838070 RH-Acked-by: Stefan Hajnoczi From: Marc-André Lureau The q pointer is updated when the mbuf data is moved from m_dat to m_ext. m_ext buffer may also be realloc()'ed and moved during m_cat(): q should also be updated in this case. Reported-by: Aviv Sasson Signed-off-by: Marc-André Lureau Reviewed-by: Samuel Thibault (cherry picked from libslirp commit 9bd6c5913271eabcb7768a58197ed3301fe19f2d) Signed-off-by: Jon Maloy Signed-off-by: Danilo C. L. de Paula --- slirp/src/ip_input.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/slirp/src/ip_input.c b/slirp/src/ip_input.c index df1c846ade..0f5d522ec1 100644 --- a/slirp/src/ip_input.c +++ b/slirp/src/ip_input.c @@ -329,7 +329,7 @@ insert: q = fp->frag_link.next; m = dtom(slirp, q); - int was_ext = m->m_flags & M_EXT; + int delta = (char *)q - (m->m_flags & M_EXT ? m->m_ext : m->m_dat); q = (struct ipasfrag *)q->ipf_next; while (q != (struct ipasfrag *)&fp->frag_link) { @@ -353,8 +353,7 @@ insert: * the old buffer (in the mbuf), so we must point ip * into the new buffer. */ - if (!was_ext && m->m_flags & M_EXT) { - int delta = (char *)q - m->m_dat; + if (m->m_flags & M_EXT) { q = (struct ipasfrag *)(m->m_ext + delta); } -- 2.27.0