linux-kernel - [PATCH 1/3] x86/kexec: Correct KEXEC_BACKUP_SRC

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Date:   Thu, 27 Sep 2018 09:21:55 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Lianbo Jiang <lijiang@...hat.com>, Vivek Goyal <vgoyal@...hat.com>,
        kexec@...ts.infradead.org, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com, x86@...nel.org, akpm@...ux-foundation.org,
        dan.j.williams@...el.com, thomas.lendacky@....com,
        baiyaowei@...s.chinamobile.com, tiwai@...e.de, bp@...e.de,
        brijesh.singh@....com, dyoung@...hat.com, bhe@...hat.com
Subject: [PATCH 1/3] x86/kexec: Correct KEXEC_BACKUP_SRC_END off-by-one error

From: Bjorn Helgaas <bhelgaas@...gle.com>

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@...gle.com>
---
 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 f327236f0fa7..5125fca472bb 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