qemu: CVE-2020-10756

An out-of-bounds read vulnerability was found in the SLiRP networking
implementation of the QEMU emulator. This flaw occurs in the
icmp6_send_echoreply() routine while replying to an ICMP echo request,
also known as ping. This flaw allows a malicious guest to leak the
contents of the host memory, resulting in possible information disclosure.
This flaw affects versions of libslirp before 4.3.1.

References:
https://nvd.nist.gov/vuln/detail/CVE-2020-10756
https://bugzilla.redhat.com/show_bug.cgi?id=1835986

Upstream patches:
c7ede54cbd

(From OE-Core rev: b6d73f9f8c055928051dc57943baf5833568d04f)

Signed-off-by: Stefan Ghinea <stefan.ghinea@windriver.com>
Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/qemu/qemu.inc

@@ -40,6 +40,7 @@ SRC_URI = "https://download.qemu.org/${BPN}-${PV}.tar.xz \
            file://CVE-2020-13765.patch \
            file://CVE-2020-10702.patch \
            file://CVE-2020-16092.patch \
+           file://CVE-2020-10756.patch \
 	   "
 UPSTREAM_CHECK_REGEX = "qemu-(?P<pver>\d+(\.\d+)+)\.tar"
 

meta/recipes-devtools/qemu/qemu/CVE-2020-10756.patch

@@ -0,0 +1,40 @@
+From c7ede54cbd2e2b25385325600958ba0124e31cc0 Mon Sep 17 00:00:00 2001
+From: Ralf Haferkamp <rhafer@suse.com>
+Date: Fri, 3 Jul 2020 14:51:16 +0200
+Subject: [PATCH] Drop bogus IPv6 messages
+
+Drop IPv6 message shorter than what's mentioned in the payload
+length header (+ the size of the IPv6 header). They're invalid an could
+lead to data leakage in icmp6_send_echoreply().
+
+CVE: CVE-2020-10756
+Upstream-Status: Backport
+https://gitlab.freedesktop.org/slirp/libslirp/-/commit/c7ede54cbd2e2b25385325600958ba0124e31cc0
+
+[SG: Based on libslirp commit c7ede54cbd2e2b25385325600958ba0124e31cc0 and adjusted context]
+Signed-off-by: Stefan Ghinea <stefan.ghinea@windriver.com>
+---
+ slirp/src/ip6_input.c | 7 +++++++
+ 1 file changed, 7 insertions(+)
+
+diff --git a/slirp/src/ip6_input.c b/slirp/src/ip6_input.c
+index d9d2b7e9..0f2b1785 100644
+--- a/slirp/src/ip6_input.c
++++ b/slirp/src/ip6_input.c
+@@ -49,6 +49,13 @@ void ip6_input(struct mbuf *m)
+         goto bad;
+     }
+ 
++    // Check if the message size is big enough to hold what's
++    // set in the payload length header. If not this is an invalid
++    // packet
++    if (m->m_len < ntohs(ip6->ip_pl) + sizeof(struct ip6)) {
++        goto bad;
++    }
++
+     /* check ip_ttl for a correct ICMP reply */
+     if (ip6->ip_hl == 0) {
+         icmp6_send_error(m, ICMP6_TIMXCEED, ICMP6_TIMXCEED_INTRANS);
+-- 
+2.17.1
+