gnu: qemu: Fix CVE-2018-7550.

* gnu/packages/patches/qemu-CVE-2018-7550.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/virtualization.scm (qemu)[source]: Use it.

gnu/local.mk

@@ -1061,6 +1061,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/python-unittest2-python3-compat.patch	\
   %D%/packages/patches/python-unittest2-remove-argparse.patch	\
   %D%/packages/patches/python-waitress-fix-tests.patch		\
+  %D%/packages/patches/qemu-CVE-2018-7550.patch			\
   %D%/packages/patches/qt4-ldflags.patch			\
   %D%/packages/patches/qtbase-use-TZDIR.patch			\
   %D%/packages/patches/qtscript-disable-tests.patch		\

gnu/packages/patches/qemu-CVE-2018-7550.patch

@@ -0,0 +1,66 @@
+Fix CVE-2018-7550:
+
+https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-7550
+
+Patch copied from upstream source repository:
+
+https://git.qemu.org/?p=qemu.git;a=patch;h=2a8fcd119eb7c6bb3837fc3669eb1b2dfb31daf8
+
+From 2a8fcd119eb7c6bb3837fc3669eb1b2dfb31daf8 Mon Sep 17 00:00:00 2001
+From: Jack Schwartz <jack.schwartz@oracle.com>
+Date: Thu, 21 Dec 2017 09:25:15 -0800
+Subject: [PATCH] multiboot: bss_end_addr can be zero
+
+The multiboot spec (https://www.gnu.org/software/grub/manual/multiboot/),
+section 3.1.3, allows for bss_end_addr to be zero.
+
+A zero bss_end_addr signifies there is no .bss section.
+
+Suggested-by: Daniel Kiper <daniel.kiper@oracle.com>
+Signed-off-by: Jack Schwartz <jack.schwartz@oracle.com>
+Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
+Reviewed-by: Prasad J Pandit <pjp@fedoraproject.org>
+Signed-off-by: Kevin Wolf <kwolf@redhat.com>
+---
+ hw/i386/multiboot.c | 18 ++++++++++--------
+ 1 file changed, 10 insertions(+), 8 deletions(-)
+
+diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
+index 46d9c68bf5..bb8d8e4629 100644
+--- a/hw/i386/multiboot.c
++++ b/hw/i386/multiboot.c
+@@ -233,12 +233,6 @@ int load_multiboot(FWCfgState *fw_cfg,
+         mh_entry_addr = ldl_p(header+i+28);
+ 
+         if (mh_load_end_addr) {
+-            if (mh_bss_end_addr < mh_load_addr) {
+-                fprintf(stderr, "invalid mh_bss_end_addr address\n");
+-                exit(1);
+-            }
+-            mb_kernel_size = mh_bss_end_addr - mh_load_addr;
+-
+             if (mh_load_end_addr < mh_load_addr) {
+                 fprintf(stderr, "invalid mh_load_end_addr address\n");
+                 exit(1);
+@@ -249,8 +243,16 @@ int load_multiboot(FWCfgState *fw_cfg,
+                 fprintf(stderr, "invalid kernel_file_size\n");
+                 exit(1);
+             }
+-            mb_kernel_size = kernel_file_size - mb_kernel_text_offset;
+-            mb_load_size = mb_kernel_size;
++            mb_load_size = kernel_file_size - mb_kernel_text_offset;
++        }
++        if (mh_bss_end_addr) {
++            if (mh_bss_end_addr < (mh_load_addr + mb_load_size)) {
++                fprintf(stderr, "invalid mh_bss_end_addr address\n");
++                exit(1);
++            }
++            mb_kernel_size = mh_bss_end_addr - mh_load_addr;
++        } else {
++            mb_kernel_size = mb_load_size;
+         }
+ 
+         /* Valid if mh_flags sets MULTIBOOT_HEADER_HAS_VBE.
+-- 
+2.17.0
+

gnu/packages/virtualization.scm

@@ -88,6 +88,7 @@ (define-public qemu
              (method url-fetch)
              (uri (string-append "https://download.qemu.org/qemu-"
                                  version ".tar.xz"))
+             (patches (search-patches "qemu-CVE-2018-7550.patch"))
              (sha256
               (base32
                "11l6cs6mib16rgdrnqrhkqs033fjik316gkgfz3asbmxz38lalca"))))