linux-ext4 - Re: [PATCH v2] ext4: ext4_fill_super shouldn't return 0 on corruption

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Date:	Thu, 18 Nov 2010 09:42:57 +0100 (CET)
From:	Lukas Czerner <lczerner@...hat.com>
To:	"Darrick J. Wong" <djwong@...ibm.com>
cc:	Lukas Czerner <lczerner@...hat.com>,
	linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH v2] ext4: ext4_fill_super shouldn't return 0 on
 corruption

On Tue, 16 Nov 2010, Darrick J. Wong wrote:

> On Tue, Nov 16, 2010 at 01:56:31PM +0100, Lukas Czerner wrote:
> > On Mon, 15 Nov 2010, Darrick J. Wong wrote:
> > 
> > > At the start of ext4_fill_super, ret is set to -EINVAL, and any failure path
> > > out of that function returns ret.  However, the generic_check_addressable
> > > clause sets ret = 0 (if it passes), which means that a subsequent failure (e.g.
> > > a group checksum error) returns 0 even though the mount should fail.  This
> > > causes vfs_kern_mount in turn to think that the mount succeeded, leading to an
> > > oops.
> > > 
> > > A simple fix is to avoid using ret for the generic_check_addressable check,
> > > which was last changed in commit 30ca22c70e3ef0a96ff84de69cd7e8561b416cb2.
> > > 
> > > v2: Return -EFBIG in the error case, per Eric Sandeen's suggestion.
> > > 
> > > Signed-off-by: Darrick J. Wong <djwong@...ibm.com>
> > > ---
> > > 
> > >  fs/ext4/super.c |    6 +++---
> > >  1 files changed, 3 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> > > index 40131b7..120c034 100644
> > > --- a/fs/ext4/super.c
> > > +++ b/fs/ext4/super.c
> > > @@ -3257,13 +3257,13 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
> > >  	 * Test whether we have more sectors than will fit in sector_t,
> > >  	 * and whether the max offset is addressable by the page cache.
> > >  	 */
> > > -	ret = generic_check_addressable(sb->s_blocksize_bits,
> > > -					ext4_blocks_count(es));
> > > -	if (ret) {
> > > +	if (generic_check_addressable(sb->s_blocksize_bits,
> > > +				      ext4_blocks_count(es))) {
> > >  		ext4_msg(sb, KERN_ERR, "filesystem"
> > >  			 " too large to mount safely on this system");
> > >  		if (sizeof(sector_t) < 8)
> > >  			ext4_msg(sb, KERN_WARNING, "CONFIG_LBDAF not enabled");
> > > +		ret = -EFBIG;
> > >  		goto failed_mount;
> > >  	}
> > >  
> > > --
> > > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> > > the body of a message to majordomo@...r.kernel.org
> > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > > 
> > 
> > Hi,
> > 
> > the untested diff below seems like a more general solution to me,
> > since it allows to return the actual error from
> > generic_check_addressable().
> 
> It seems to work ok for me, so:
> 
> Acked-by: Darrick J. Wong <djwong@...ibm.com>
> 
> I will make the same change to ext3.
> 
> --D

Oh, so you want me to post it as a patch ? Ok, then I'll use the same
comment (hope it is ok).

Thanks!

-Lukas

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