CVE: CVE-2018-11806
Upstream-Status: Backport

https://lists.gnu.org/archive/html/qemu-devel/2018-06/msg01012.html

From dc21a9d2951f0a2a7e63633e2b5c68c54e4edc4b Mon Sep 17 00:00:00 2001
From: Jeremy Puhlman <jpuhlman@mvista.com>
Date: Thu, 14 Jun 2018 01:28:49 +0000
Subject: [PATCH] CVE-2018-11806 QEMU: slirp: heap buffer overflow

Subject: [Qemu-devel] [PATCH 1/2] slirp: correct size computation while concatenating mbuf
Date:	Tue, 5 Jun 2018 23:38:35 +0530
From: Prasad J Pandit <address@hidden>

While reassembling incoming fragmented datagrams, 'm_cat' routine
extends the 'mbuf' buffer, if it has insufficient room. It computes
a wrong buffer size, which leads to overwriting adjacent heap buffer
area. Correct this size computation in m_cat.

Reported-by: ZDI Disclosures <address@hidden>
Signed-off-by: Prasad J Pandit <address@hidden>
---
 slirp/mbuf.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Signed-off-by: Jeremy Puhlman <jpuhlman@mvista.com>
---
 slirp/mbuf.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/slirp/mbuf.c b/slirp/mbuf.c
index 5ff2455..7fb4501 100644
--- a/slirp/mbuf.c
+++ b/slirp/mbuf.c
@@ -138,7 +138,7 @@ m_cat(struct mbuf *m, struct mbuf *n)
 	 * If there's no room, realloc
 	 */
 	if (M_FREEROOM(m) < n->m_len)
-		m_inc(m,m->m_size+MINCSIZE);
+               m_inc(m, m->m_len + n->m_len);
 
 	memcpy(m->m_data+m->m_len, n->m_data, n->m_len);
 	m->m_len += n->m_len;
@@ -158,12 +158,12 @@ m_inc(struct mbuf *m, int size)
 
         if (m->m_flags & M_EXT) {
 	  datasize = m->m_data - m->m_ext;
-          m->m_ext = g_realloc(m->m_ext, size);
+          m->m_ext = g_realloc(m->m_ext, size + datasize);
 	  m->m_data = m->m_ext + datasize;
         } else {
 	  char *dat;
 	  datasize = m->m_data - m->m_dat;
-          dat = g_malloc(size);
+          dat = g_malloc(size + datasize);
 	  memcpy(dat, m->m_dat, m->m_size);
 
 	  m->m_ext = dat;
@@ -171,7 +171,7 @@ m_inc(struct mbuf *m, int size)
 	  m->m_flags |= M_EXT;
         }
 
-        m->m_size = size;
+        m->m_size = size + datasize;
 
 }
 
-- 
2.13.3

