linux-kernel - Re: [PATCH] ext4: fix possible overflow in ext4_trim

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Message-ID: <alpine.LFD.2.00.1101101221570.3095@dhcp-lab-213.englab.brq.redhat.com>
Date:	Mon, 10 Jan 2011 12:25:05 +0100 (CET)
From:	Lukas Czerner <lczerner@...hat.com>
To:	"Ted Ts'o" <tytso@....edu>
cc:	Lukas Czerner <lczerner@...hat.com>, linux-kernel@...r.kernel.org,
	sandeen@...hat.com
Subject: Re: [PATCH] ext4: fix possible overflow in ext4_trim_fs()

On Mon, 20 Dec 2010, Ted Ts'o wrote:

> On Thu, Nov 25, 2010 at 03:11:17PM +0100, Lukas Czerner wrote:
> > When determining last group through ext4_get_group_no_and_offset() the
> > result may be wrong in cases when range->start and range-len are too
> > big, because it may overflow when summing up those two numbers.
> > 
> > Fix that by checking range->len and limit its value to
> > ext4_blocks_count(). This commit was tested by myself with expected
> > result.
> > 
> > Signed-off-by: Lukas Czerner <lczerner@...hat.com>
> 
> Added to the ext4 patch queue.  Thanks for the ping.
> 
>       	     	  		       	   - Ted
> 

Hi Ted,

Actually the patch is not enough, there is still a possibility for
overflow to happen. Jan Kara notice the same bug in ext3 batched discard
implementation. I am sorry for this, I'll sen updated patch ASAP.

-Lukas
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