linux-kernel - Re: [PATCH 1/2] ext3: fix a bug accessing freed memory in ext3

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Date:	Mon, 27 Oct 2008 09:11:08 +0100
From:	Jan Kara <jack@...e.cz>
To:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
Cc:	Vegard Nossum <vegard.nossum@...il.com>,
	Theodore Tso <tytso@....edu>, Jan Kara <jack@....cz>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Al Viro <viro@...iv.linux.org.uk>, linux-ext4@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Ingo Molnar <mingo@...e.hu>,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] ext3: fix a bug accessing freed memory in ext3_abort

> Hi Vegard,
> 
> Vegard Nossum wrote:
> 
> > commit 2d7c820e56ce83b23daee9eb5343730fb309418e
> > Author: Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
> > Date:   Wed Oct 22 14:15:01 2008 -0700
> > 
> >     ext3: add checks for errors from jbd
> > 
> > introduces a regression which was discovered by kmemcheck:
> 
> Thank you for reporting this regression.  It's my fault.
> I send patches to fix.
> 
> Regards,
> 
> 
> Subject: [PATCH 1/2] ext3: fix a bug accessing freed memory in ext3_abort
> 
> Vegard Nossum reported a bug which accesses freed memory.  When
> journal has been aborted, ext3_put_super() calls ext3_abort() after
> freeing the journal_t object, and then ext3_abort() accesses it.
> This patch fix it.
> 
> Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
  The patch looks fine. Acked-by: Jan Kara <jack@...e.cz>

								Honza
> ---
>  fs/ext3/super.c |   10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> Index: linux-2.6.28-rc2/fs/ext3/super.c
> ===================================================================
> --- linux-2.6.28-rc2.orig/fs/ext3/super.c
> +++ linux-2.6.28-rc2/fs/ext3/super.c
> @@ -281,7 +281,8 @@ void ext3_abort (struct super_block * sb
>  	EXT3_SB(sb)->s_mount_state |= EXT3_ERROR_FS;
>  	sb->s_flags |= MS_RDONLY;
>  	EXT3_SB(sb)->s_mount_opt |= EXT3_MOUNT_ABORT;
> -	journal_abort(EXT3_SB(sb)->s_journal, -EIO);
> +	if (EXT3_SB(sb)->s_journal)
> +		journal_abort(EXT3_SB(sb)->s_journal, -EIO);
>  }
>  
>  void ext3_warning (struct super_block * sb, const char * function,
> @@ -390,11 +391,14 @@ static void ext3_put_super (struct super
>  {
>  	struct ext3_sb_info *sbi = EXT3_SB(sb);
>  	struct ext3_super_block *es = sbi->s_es;
> -	int i;
> +	int i, err;
>  
>  	ext3_xattr_put_super(sb);
> -	if (journal_destroy(sbi->s_journal) < 0)
> +	err = journal_destroy(sbi->s_journal);
> +	sbi->s_journal = NULL;
> +	if (err < 0)
>  		ext3_abort(sb, __func__, "Couldn't clean up the journal");
> +
>  	if (!(sb->s_flags & MS_RDONLY)) {
>  		EXT3_CLEAR_INCOMPAT_FEATURE(sb, EXT3_FEATURE_INCOMPAT_RECOVER);
>  		es->s_state = cpu_to_le16(sbi->s_mount_state);
> 
-- 
Jan Kara <jack@...e.cz>
SuSE CR Labs
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