From 9ea892729b9c77eaf7b923da8a3e370dbb022e6e Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Thu, 26 Jul 2018 16:24:48 +0200
Subject: [PATCH 6/8] multiboot: Check validity of mh_header_addr

RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <20180726162448.22072-7-kwolf@redhat.com>
Patchwork-id: 81515
O-Subject: [RHEL-7.6/7.5.z qemu-kvm PATCH 6/6] multiboot: Check validity of mh_header_addr
Bugzilla: 1549822
RH-Acked-by: John Snow <jsnow@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

I couldn't find a case where this prevents something bad from happening
that isn't already caught by other checks, but let's err on the safe
side and check that mh_header_addr is as expected.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Jack Schwartz <jack.schwartz@oracle.com>
(cherry picked from commit dbf2dce7aabb7723542bd182175904846d70b0f9)
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/i386/multiboot.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
index 6f489a5..e1f6e56 100644
--- a/hw/i386/multiboot.c
+++ b/hw/i386/multiboot.c
@@ -208,6 +208,10 @@ int load_multiboot(FWCfgState *fw_cfg,
             error_report("invalid load_addr address");
             exit(1);
         }
+        if (mh_header_addr - mh_load_addr > i) {
+            error_report("invalid header_addr address");
+            exit(1);
+        }
 
         uint32_t mb_kernel_text_offset = i - (mh_header_addr - mh_load_addr);
         uint32_t mb_load_size = 0;
-- 
1.8.3.1