linux-ext4 - Re: [PATCH 7/7] libext2fs: enforce the block group descriptor size in ext2fs

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Message-ID: <20120731200918.GF32228@thunk.org>
Date:	Tue, 31 Jul 2012 16:09:18 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Andreas Dilger <adilger@...mcloud.com>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	"tony@...eyournoodle.com" <tony@...eyournoodle.com>
Subject: Re: [PATCH 7/7] libext2fs: enforce the block group descriptor size
 in ext2fs_open()

On Tue, Jul 31, 2012 at 11:38:47AM -0700, Andreas Dilger wrote:
> > +    /* Enforce the block group descriptor size */
> > +    if (fs->super->s_feature_incompat & EXT4_FEATURE_INCOMPAT_64BIT) {
> > +        if (fs->super->s_desc_size != EXT2_MIN_DESC_SIZE_64BIT) {
> 
> It doesn't necessarily make sense to limit this to the minimum size, only that it is at least the minimum size. 

I'm not at all convinced that the ext2fs library will do the right
thing if the block group size is larger than what we expect.  At the
very least we need to make sure it is a power of two, but even so I'd
want to audit the code and do some experiments before I would hang my
hat on this actually working correctly...

					- Ted
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