linux-kernel - [Patch] kexec: remove KMSG_DUMP_KEXEC (was Re: Query about kdump_msg hook into crash

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Message-ID: <20110201081313.GC21239@cr0.nay.redhat.com>
Date:	Tue, 1 Feb 2011 16:13:13 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	Américo Wang <xiyou.wangcong@...il.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	kosaki.motohiro@...fujitsu.com,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Jarod Wilson <jwilson@...hat.com>, akpm@...ux-foundation.org
Subject: [Patch] kexec: remove KMSG_DUMP_KEXEC (was Re: Query about kdump_msg
 hook into crash_kexec())

On Tue, Feb 01, 2011 at 03:38:53PM +0800, Américo Wang wrote:
>On Mon, Jan 31, 2011 at 11:33:15PM -0800, Eric W. Biederman wrote:
>>The issue is the inane call inside crash_kexec.
>>
>>It requires both a kexec kernel to be loaded and it requires you to be
>>crashing.  Given that when I audited the kmsg_dump handlers they really
>>weren't safe in a crash dump scenario we should just remove it.
>>
>
>Probably, I think we need to get rid of KMSG_DUMP_KEXEC.
>

Here we go.

--------->

KMSG_DUMP_KEXEC is useless because we already save kernel messages
inside /proc/vmcore, and it is unsafe to allow modules to do
other stuffs in a crash dump scenario.

Reported-by: Vivek Goyal <vgoyal@...hat.com>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
Signed-off-by: WANG Cong <xiyou.wangcong@...il.com>


---
diff --git a/drivers/char/ramoops.c b/drivers/char/ramoops.c
index 1a9f5f6..8653ba4 100644
--- a/drivers/char/ramoops.c
+++ b/drivers/char/ramoops.c
@@ -69,8 +69,7 @@ static void ramoops_do_dump(struct kmsg_dumper *dumper,
 	struct timeval timestamp;
 
 	if (reason != KMSG_DUMP_OOPS &&
-	    reason != KMSG_DUMP_PANIC &&
-	    reason != KMSG_DUMP_KEXEC)
+	    reason != KMSG_DUMP_PANIC)
 		return;
 
 	/* Only dump oopses if dump_oops is set */
diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c
index e3e40f4..56eac4e 100644
--- a/drivers/mtd/mtdoops.c
+++ b/drivers/mtd/mtdoops.c
@@ -308,8 +308,7 @@ static void mtdoops_do_dump(struct kmsg_dumper *dumper,
 	char *dst;
 
 	if (reason != KMSG_DUMP_OOPS &&
-	    reason != KMSG_DUMP_PANIC &&
-	    reason != KMSG_DUMP_KEXEC)
+	    reason != KMSG_DUMP_PANIC)
 		return;
 
 	/* Only dump oopses if dump_oops is set */
diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h
index 2a0d7d6..05fa2a9 100644
--- a/include/linux/kmsg_dump.h
+++ b/include/linux/kmsg_dump.h
@@ -17,7 +17,6 @@
 enum kmsg_dump_reason {
 	KMSG_DUMP_OOPS,
 	KMSG_DUMP_PANIC,
-	KMSG_DUMP_KEXEC,
 	KMSG_DUMP_RESTART,
 	KMSG_DUMP_HALT,
 	KMSG_DUMP_POWEROFF,
diff --git a/kernel/kexec.c b/kernel/kexec.c
index ec19b92..3ac0218 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -32,7 +32,6 @@
 #include <linux/console.h>
 #include <linux/vmalloc.h>
 #include <linux/swap.h>
-#include <linux/kmsg_dump.h>
 
 #include <asm/page.h>
 #include <asm/uaccess.h>
@@ -1078,8 +1077,6 @@ void crash_kexec(struct pt_regs *regs)
 		if (kexec_crash_image) {
 			struct pt_regs fixed_regs;
 
-			kmsg_dump(KMSG_DUMP_KEXEC);
-
 			crash_setup_regs(&fixed_regs, regs);
 			crash_save_vmcoreinfo();
 			machine_crash_shutdown(&fixed_regs);
--
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