linux-ext4 - [PATHC] Fix for ext2 reservation (Re: -mm merge plans for 2.6.23)

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Date:	Tue, 10 Jul 2007 15:15:57 -0700
From:	Badari Pulavarty <pbadari@...ibm.com>
To:	Martin Bligh <mbligh@...igh.org>,
	Alexey Dobriyan <adobriyan@...il.com>, Greg KH <greg@...ah.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hugh@...itas.com>,
	Jeremy Orlow <jorlow@...gle.com>,
	Nick Piggin <piggin@...erone.com.au>,
	Mingming Cao <cmm@...ibm.com>,
	ext4 <linux-ext4@...r.kernel.org>,
	ltc-kernel <ltc-kernel@...ux.ibm.com>, stable@...nel.org
Subject: [PATHC] Fix for ext2 reservation (Re: -mm merge plans for 2.6.23)

On Tue, 2007-07-10 at 12:39 -0700, Martin Bligh wrote:
> Andrew Morton wrote:
> > 
> > Begin forwarded message:
> > 
> > Date: Tue, 10 Jul 2007 21:49:23 +0400
> > From: Alexey Dobriyan <adobriyan@...il.com>
> > To: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org
> > Subject: ext2 reservations (Re: -mm merge plans for 2.6.23)
> > 
> > 
> >> ext2-reservations.patch
> >>
> >>  Still needs decent testing.
> > 
> > Was this oops silently fixed?
> > http://lkml.org/lkml/2007/3/2/138
> > 2.6.21-rc2-mm1: EIP is at ext2_discard_reservation+0x1c/0x52
> > 
> > I still have that ext2 partition backed up.
> 
> Now I'm confused - I thought there was a latent issue there, and
> then we went back and revisited it, and we decided there wasn't ;-(

Well, I looked at the problem now and here is the fix :)

Greg, Please consider this for stable release also.

Thanks,
Badari

ext2 reservation fix - Alexey Dobriyan reported ext2 discard
reservation panic while ago (http://lkml.org/lkml/2007/3/2/138).
If ext2_new_inode() fails for any reason it would end up calling 
ext2_discard_reservation() (due to last iput). Normally, it does
nothing since we don't have a reservation window structure
allocated. But the NULL pointer check wouldn't work with  slab 
poisioning, and causes oops.

Fix is to initialize i_block_alloc_info to NULL in ext2_alloc_inode()
code instead of assuming that it would be NULL. Same fix already
exists in ext3 and ext4.

Signed-off-by: Badari Pulavarty <pbadari@...ibm.com>

 fs/ext2/super.c |    1 +
 1 file changed, 1 insertion(+)

Index: linux-2.6.22/fs/ext2/super.c
===================================================================
--- linux-2.6.22.orig/fs/ext2/super.c	2007-07-08 16:32:17.000000000 -0700
+++ linux-2.6.22/fs/ext2/super.c	2007-07-10 16:36:42.000000000 -0700
@@ -147,6 +147,7 @@ static struct inode *ext2_alloc_inode(st
 	ei->i_acl = EXT2_ACL_NOT_CACHED;
 	ei->i_default_acl = EXT2_ACL_NOT_CACHED;
 #endif
+	ei->i_block_alloc_info = NULL;
 	ei->vfs_inode.i_version = 1;
 	return &ei->vfs_inode;
 }


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