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From dea2f95979cc0ba0c36f07b8e9cc709bd1ef1eb4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= <philmd@redhat.com>
Date: Fri, 17 Jan 2020 12:00:35 +0100
Subject: [PATCH 1/3] tcp_emu: Fix oob access
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RH-Author: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: <20200117120037.12800-2-philmd@redhat.com>
Patchwork-id: 93395
O-Subject: [RHEL-7.7.z qemu-kvm + RHEL-7.8 qemu-kvm + RHEL-7.9 qemu-kvm PATCH v2 1/3] tcp_emu: Fix oob access
Bugzilla: 1791560
RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Thomas Huth <thuth@redhat.com>

From: Samuel Thibault <samuel.thibault@ens-lyon.org>

The main loop only checks for one available byte, while we sometimes
need two bytes.

(cherry picked from libslirp commit 2655fffed7a9e765bcb4701dd876e9dab975f289)
[PMD: backported with style conflicts,
      CHANGELOG.md absent in downstream]
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 slirp/tcp_subr.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c
index d49a366..70a4c83 100644
--- a/slirp/tcp_subr.c
+++ b/slirp/tcp_subr.c
@@ -837,6 +837,9 @@ tcp_emu(struct socket *so, struct mbuf *m)
 				break;
 
 			 case 5:
+				if (bptr == m->m_data + m->m_len - 1)
+					return 1; /* We need two bytes */
+
 				/*
 				 * The difference between versions 1.0 and
 				 * 2.0 is here. For future versions of
@@ -852,6 +855,10 @@ tcp_emu(struct socket *so, struct mbuf *m)
 				/* This is the field containing the port
 				 * number that RA-player is listening to.
 				 */
+
+				if (bptr == m->m_data + m->m_len - 1)
+					return 1; /* We need two bytes */
+
 				lport = (((u_char*)bptr)[0] << 8)
 				+ ((u_char *)bptr)[1];
 				if (lport < 6970)
-- 
1.8.3.1