qemu: Security Advisory - qemu - CVE-2019-15890

Backporting patch from
https://gitlab.freedesktop.org/slirp/libslirp/commit/c5927943
to solve CVE-2019-15890.

(From OE-Core rev: 2cccc685cc6359595ef3e943cd03290d8c8866f0)

Signed-off-by: Li Zhou <li.zhou@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/qemu/qemu.inc

@@ -23,6 +23,7 @@ SRC_URI = "https://download.qemu.org/${BPN}-${PV}.tar.xz \
            file://0008-linux-user-Fix-webkitgtk-hangs-on-32-bit-x86-target.patch \
            file://0009-Fix-webkitgtk-builds.patch \
            file://0010-configure-Add-pkg-config-handling-for-libgcrypt.patch \
+           file://CVE-2019-15890.patch \
            "
 UPSTREAM_CHECK_REGEX = "qemu-(?P<pver>\d+(\.\d+)+)\.tar"
 

meta/recipes-devtools/qemu/qemu/CVE-2019-15890.patch

@@ -0,0 +1,48 @@
+From 4fc0d23e8f6d795c679623d2ed2cbe6a7a17b9c7 Mon Sep 17 00:00:00 2001
+From: Li Zhou <li.zhou@windriver.com>
+Date: Tue, 10 Sep 2019 20:02:15 -0700
+Subject: [PATCH] ip_reass: Fix use after free
+
+Using ip_deq after m_free might read pointers from an allocation reuse.
+
+This would be difficult to exploit, but that is still related with
+CVE-2019-14378 which generates fragmented IP packets that would trigger this
+issue and at least produce a DoS.
+
+Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
+
+Upstream-Status: Backport
+CVE: CVE-2019-15890
+Signed-off-by: Li Zhou <li.zhou@windriver.com>
+---
+ slirp/src/ip_input.c | 6 ++++--
+ 1 file changed, 4 insertions(+), 2 deletions(-)
+
+diff --git a/slirp/src/ip_input.c b/slirp/src/ip_input.c
+index 8c75d914..c07d7d40 100644
+--- a/slirp/src/ip_input.c
++++ b/slirp/src/ip_input.c
+@@ -292,6 +292,7 @@ static struct ip *ip_reass(Slirp *slirp, struct ip *ip, struct ipq *fp)
+      */
+     while (q != (struct ipasfrag *)&fp->frag_link &&
+            ip->ip_off + ip->ip_len > q->ipf_off) {
++        struct ipasfrag *prev;
+         i = (ip->ip_off + ip->ip_len) - q->ipf_off;
+         if (i < q->ipf_len) {
+             q->ipf_len -= i;
+@@ -299,9 +300,10 @@ static struct ip *ip_reass(Slirp *slirp, struct ip *ip, struct ipq *fp)
+             m_adj(dtom(slirp, q), i);
+             break;
+         }
++        prev = q;
+         q = q->ipf_next;
+-        m_free(dtom(slirp, q->ipf_prev));
+-        ip_deq(q->ipf_prev);
++        ip_deq(prev);
++        m_free(dtom(slirp, prev));
+     }
+ 
+ insert:
+-- 
+2.23.0
+