[PATCH AUTOSEL 4.14 095/115] x86/kexec: Correct KEXEC_BACKUP_SRC_END off-by-one error

[Sasha Levin]

From: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>

[ Upstream commit 51fbf14f2528a8c6401290e37f1c893a2412f1d3 ]

The only use of KEXEC_BACKUP_SRC_END is as an argument to
walk_system_ram_res():

  int crash_load_segments(struct kimage *image)
  {
    ...
    walk_system_ram_res(KEXEC_BACKUP_SRC_START, KEXEC_BACKUP_SRC_END,
                        image, determine_backup_region);

walk_system_ram_res() expects "start, end" arguments that are inclusive,
i.e., the range to be walked includes both the start and end addresses.

KEXEC_BACKUP_SRC_END was previously defined as (640 * 1024UL), which is the
first address *past* the desired 0-640KB range.

Define KEXEC_BACKUP_SRC_END as (640 * 1024UL - 1) so the KEXEC_BACKUP_SRC
region is [0-0x9ffff], not [0-0xa0000].

Fixes: dd5f726076cc ("kexec: support for kexec on panic using new system call")
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: Brijesh Singh <brijesh.singh@xxxxxxx>
CC: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxxxxx>
CC: Lianbo Jiang <lijiang@xxxxxxxxxx>
CC: Takashi Iwai <tiwai@xxxxxxx>
CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CC: Tom Lendacky <thomas.lendacky@xxxxxxx>
CC: Vivek Goyal <vgoyal@xxxxxxxxxx>
CC: baiyaowei@xxxxxxxxxxxxxxxxxxxx
CC: bhe@xxxxxxxxxx
CC: dan.j.williams@xxxxxxxxx
CC: dyoung@xxxxxxxxxx
CC: kexec@xxxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/153805811578.1157.6948388946904655969.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 arch/x86/include/asm/kexec.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index f327236f0fa71..5125fca472bb0 100644
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -67,7 +67,7 @@ struct kimage;
 
 /* Memory to backup during crash kdump */
 #define KEXEC_BACKUP_SRC_START	(0UL)
-#define KEXEC_BACKUP_SRC_END	(640 * 1024UL)	/* 640K */
+#define KEXEC_BACKUP_SRC_END	(640 * 1024UL - 1)	/* 640K */
 
 /*
  * CPU does not save ss and sp on stack if execution is already
-- 
2.20.1