linux-ext4 - [PATCH] introduce range check for extent pblock references

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Date:	Sat, 07 Feb 2009 16:36:58 +0100
From:	Thiemo Nagel <thiemo.nagel@...tum.de>
To:	Theodore Tso <tytso@....edu>
CC:	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: [PATCH] introduce range check for extent pblock references

This time I have aimed to catch all cases in which an invalid physical 
block might be used and implemented checks directly in ext_pblock() and 
idx_pblock() following the assumption that most of the times one of 
these functions is called a device access to that address will follow. 
If you think this is too heavy, I could also split the check from the 
pblock calculation, but in that case I could only guess at which of the 
several accesses to *_pblock() in extents.c a check would be necessary 
and where it wouldn't and there would be the possibility of missing 
something.

Another thing I'm unsure about is uninitialised extents, here my 
heuristic again was that ext_pblock() wouldn't be called if there was 
not an access to follow, so I didn't include a condition that would 
excempt them from the check.

The attached patch has only been mildly tested.

And I'm pretty new to linux and ext4, so there might be stupid mistakes.

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

View attachment "patch2" of type "text/plain" (16030 bytes)