linux-ext4 - [PATCH v2] ext4: add checks of block references for non-extent inodes

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Message-ID: <49C3A51C.1030201@ph.tum.de>
Date:	Fri, 20 Mar 2009 15:15:56 +0100
From:	Thiemo Nagel <thiemo.nagel@...tum.de>
To:	Theodore Ts'o <tytso@....edu>
CC:	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: [PATCH v2] ext4: add checks of block references for non-extent inodes

Dear Ted,

I'm sending an improved patch as I've come to the conclusion that the 
previous patch is too lenient in two ways:
* off-by-one in the check of the upper block limit
* it shouldn't stop when encountering a reference to block number zero 
because, if I'm not mistaken, references behind it still might be 
accessed in sparse files / when seeking behind the end of a file.

On the other hand, I decided to drop the check against 
s_first_data_block at the low end to improve performance, since the 
purpose of the patch is to prevent access to blocks outside the 
filesystem, and not to do the best-possible consistency check against 
indirect blocks, which probably is better done in fsck.

Anyways, in case you would be interested in having more checks here (eg. 
as a compile-time option), I have available a more sophisticated patch 
which also checks for non-zero block references behind the end of the file.

Kind regards,

Signed-off-by: Thiemo Nagel <thiemo.nagel@...tum.de>

View attachment "add-blockref-checks.patch2" of type "text/plain" (1880 bytes)