File 0334-Fix-heap-overflow-in-ip_reass-on-bi.patch of Package qemu.19799

From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date: Tue, 6 Aug 2019 18:16:07 -0400
Subject: Fix heap overflow in ip_reass on big packet input

When the first fragment does not fit in the preallocated buffer, q will
already be pointing to the ext buffer, so we mustn't try to update it.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
(cherry picked from commit 126c04acbabd7ad32c2b018fe10dfac2a3bc1210)
[LY: CVE-2019-14378 BSC#1143794]
Signed-off-by: Liang Yan <lyan@suse.com>
---
 slirp/ip_input.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/slirp/ip_input.c b/slirp/ip_input.c
index cdd54833a342e4146d6caa10f141..9da0298aff1042c0b54fc6a0588e 100644
--- a/slirp/ip_input.c
+++ b/slirp/ip_input.c
@@ -335,6 +335,8 @@ insert:
     q = fp->frag_link.next;
 	m = dtom(slirp, q);
 
+    int was_ext = m->m_flags & M_EXT;
+
 	q = (struct ipasfrag *) q->ipf_next;
 	while (q != (struct ipasfrag*)&fp->frag_link) {
 	  struct mbuf *t = dtom(slirp, q);
@@ -357,7 +359,7 @@ insert:
 	 * the old buffer (in the mbuf), so we must point ip
 	 * into the new buffer.
 	 */
-	if (m->m_flags & M_EXT) {
+	if (!was_ext && m->m_flags & M_EXT) {
 	  int delta = (char *)q - m->m_dat;
 	  q = (struct ipasfrag *)(m->m_ext + delta);
 	}