Fixes CVE-2019-6778:

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-6778

Patch copied from upstream source repository:

https://git.qemu.org/?p=qemu.git;a=commitdiff;h=a7104eda7dab99d0cdbd3595c211864cba415905

From a7104eda7dab99d0cdbd3595c211864cba415905 Mon Sep 17 00:00:00 2001
From: Prasad J Pandit <pjp@fedoraproject.org>
Date: Sun, 13 Jan 2019 23:29:48 +0530
Subject: [PATCH] slirp: check data length while emulating ident function

While emulating identification protocol, tcp_emu() does not check
available space in the 'sc_rcv->sb_data' buffer. It could lead to
heap buffer overflow issue. Add check to avoid it.

Reported-by: Kira <864786842@qq.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
---
 slirp/tcp_subr.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c
index 4a9a5b5edc..23a841f26e 100644
--- a/slirp/tcp_subr.c
+++ b/slirp/tcp_subr.c
@@ -634,6 +634,11 @@ tcp_emu(struct socket *so, struct mbuf *m)
 			socklen_t addrlen = sizeof(struct sockaddr_in);
 			struct sbuf *so_rcv = &so->so_rcv;
 
+			if (m->m_len > so_rcv->sb_datalen
+					- (so_rcv->sb_wptr - so_rcv->sb_data)) {
+			    return 1;
+			}
+
 			memcpy(so_rcv->sb_wptr, m->m_data, m->m_len);
 			so_rcv->sb_wptr += m->m_len;
 			so_rcv->sb_rptr += m->m_len;
-- 
2.20.1

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<div class='path'>path: <a href='/guix/log/?id=5a1ac6138d31f5e48c273b4f9292292d76d7432a'>root</a>/<a href='/guix/log/tests?id=5a1ac6138d31f5e48c273b4f9292292d76d7432a'>tests</a>/<a href='/guix/log/tests/opam.scm?id=5a1ac6138d31f5e48c273b4f9292292d76d7432a'>opam.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/opam.scm?id=5a1ac6138d31f5e48c273b4f9292292d76d7432a&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-09-04 17:25:11 +0200'>2018-09-04</span></td><td><a href='/guix/commit/tests/opam.scm?id=ca719424455465fca4b872c371daf2a46de88b33'>Switch to Guile-Gcrypt.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-07-10 10:11:01 +0200'>2018-07-10</span></td><td><a href='/guix/commit/tests/opam.scm?id=b24443bff9f9f3f36353eea2ef35e6dc3745a417'>guix: Add opam importer.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>