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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.
CVE: CVE-2018-7550
Upstream-Status: Backport [https://git.qemu.org/?p=qemu.git;a=commitdiff;h=2a8fcd119eb7c6bb3837fc3669eb1b2dfb31daf8]
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>
Signed-off-by: Jagadeesh Krishnanjanappa <jkrishnanjanappa@mvista.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.
--
2.13.3
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