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Fix CVE-2018-11806:
https://lists.gnu.org/archive/html/qemu-devel/2018-06/msg01012.html
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-11806
Patch copied from upstream source repository:
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=864036e251f54c99d31df124aad7f34f01f5344c
From 864036e251f54c99d31df124aad7f34f01f5344c Mon Sep 17 00:00:00 2001
From: Prasad J Pandit <pjp@fedoraproject.org>
Date: Tue, 5 Jun 2018 23:38:35 +0530
Subject: [PATCH] slirp: correct size computation while concatenating mbuf
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 <zdi-disclosures@trendmicro.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
---
slirp/mbuf.c | 11 +++++------
slirp/mbuf.h | 8 +++-----
2 files changed, 8 insertions(+), 11 deletions(-)
diff --git a/slirp/mbuf.c b/slirp/mbuf.c
index 5ff24559fd..18cbf759a7 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;
@@ -147,7 +147,7 @@ m_cat(struct mbuf *m, struct mbuf *n)
}
-/* make m size bytes large */
+/* make m 'size' bytes large from m_data */
void
m_inc(struct mbuf *m, int size)
{
@@ -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;
@@ -171,8 +171,7 @@ m_inc(struct mbuf *m, int size)
m->m_flags |= M_EXT;
}
- m->m_size = size;
-
+ m->m_size = size + datasize;
}
diff --git a/slirp/mbuf.h b/slirp/mbuf.h
index 893601ff9d..33b84485d6 100644
--- a/slirp/mbuf.h
+++ b/slirp/mbuf.h
@@ -33,8 +33,6 @@
#ifndef MBUF_H
#define MBUF_H
-#define MINCSIZE 4096 /* Amount to increase mbuf if too small */
-
/*
* Macros for type conversion
* mtod(m,t) - convert mbuf pointer to data pointer of correct type
@@ -72,11 +70,11 @@ struct mbuf {
struct mbuf *m_prevpkt; /* Flags aren't used in the output queue */
int m_flags; /* Misc flags */
- int m_size; /* Size of data */
+ int m_size; /* Size of mbuf, from m_dat or m_ext */
struct socket *m_so;
- caddr_t m_data; /* Location of data */
- int m_len; /* Amount of data in this mbuf */
+ caddr_t m_data; /* Current location of data */
+ int m_len; /* Amount of data in this mbuf, from m_data */
Slirp *slirp;
bool resolution_requested;
--
2.17.1
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