Date:	Wed, 30 Jan 2008 15:17:57 -0800
From:	Mingming Cao <cmm@...ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Fw: [Bugme-new] [Bug 9849] New: NULL pointer deref in
	journal_wait_on_commit_record

On Wed, 2008-01-30 at 12:00 -0800, Andrew Morton wrote:
> 
> Begin forwarded message:
> 
> Date: Wed, 30 Jan 2008 03:24:08 -0800 (PST)
> From: bugme-daemon@...zilla.kernel.org
> To: bugme-new@...ts.osdl.org
> Subject: [Bugme-new] [Bug 9849] New: NULL pointer deref in journal_wait_on_commit_record
> 
> 
> http://bugzilla.kernel.org/show_bug.cgi?id=9849
> 
>            Summary: NULL pointer deref in journal_wait_on_commit_record
>            Product: File System
>            Version: 2.5
>      KernelVersion: 2.6.24-03997-g85004cc
>           Platform: All
>         OS/Version: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: ext4
>         AssignedTo: fs_ext4@...nel-bugs.osdl.org
>         ReportedBy: snakebyte@....de
> 
> 
> Latest working kernel version: -
> Earliest failing kernel version: 2.6.24-03863-g0ba6c33
> Distribution: Ubuntu
> Problem Description:
> 
> using a corrupted image causes an oops in unmount, seems as if
> journal_wait_on_commit_record() gets passed a NULL pointer
> 

The buufer head pointer passed to journal_wait_on_commit_record() could
be NULL if the previous journal_submit_commit_record() failed or journal
has already aborted.

Looking at the jbd2 debug messages, before the oops happen, the jbd2 is
aborted due to trying to access the next log block beyond the end of
device. This might be caused by using a corrupted image.

We need to check the error returns from journal_submit_commit_record()
and avoid calling journal_wait_on_commit_record() in the failure case.

Signed-off-by: Mingming Cao <cmm@...ibm.com>
The buufer head pointer passed to journal_wait_on_commit_record()
could be NULL if the previous journal_submit_commit_record() failed
or journal has already aborted.

We need to check the error returns from journal_submit_commit_record()
and avoid calling journal_wait_on_commit_record() in the failure case.

Signed-off-by: Mingming Cao <cmm@...ibm.com>
---
 fs/jbd2/commit.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-2.6.24-rc8/fs/jbd2/commit.c
===================================================================
--- linux-2.6.24-rc8.orig/fs/jbd2/commit.c	2008-01-30 14:12:10.000000000 -0800
+++ linux-2.6.24-rc8/fs/jbd2/commit.c	2008-01-30 15:09:50.000000000 -0800
@@ -872,7 +872,8 @@ wait_for_iobuf:
 		if (err)
 			__jbd2_journal_abort_hard(journal);
 	}
-	err = journal_wait_on_commit_record(cbh);
+	if (!err && !is_journal_aborted(journal))
+		err = journal_wait_on_commit_record(cbh);
 
 	if (err)
 		jbd2_journal_abort(journal, err);


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