linux-ext4 - Re: [PATCH v3] ext4: fix possible overflow in ext4_trim

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Date:	Mon, 10 Oct 2011 12:47:11 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Lukas Czerner <lczerner@...hat.com>
Cc:	linux-ext4@...r.kernel.org, tm@....ma
Subject: Re: [PATCH v3] ext4: fix possible overflow in ext4_trim_fs()

On Wed, Sep 07, 2011 at 05:52:57PM +0200, Lukas Czerner wrote:
> The overflow can happen when we are calling get_group_no_and_offset()
> which stores the result of do_div() in 32 bit long type. However the
> result might be bigger than that if big blocknr is passed in. This will
> most likely happen when calling FITRIM with the default argument len =
> ULLONG_MAX.
> 
> Fix this by using "end" variable instead of "start+len" as it is easier
> to get right and specifically check that the end is not beyond the end
> of the file system, so we are sure that the result of
> get_group_no_and_offset() will not overflow. Otherwise truncate it to
> the size of the file system.
> 
> Signed-off-by: Lukas Czerner <lczerner@...hat.com>

Hi Lukas,

Since I've merged the bigalloc patches that uses clusters instead of
blocks for various file system parameters.  I made a quick attempt to
port your patch, and it wasn't obvious (and I don't have your testing
framework).  Could you do me a favor and forward port your patch to
either the dev or master branch on the ext4 github repository?

Thanks!!

					- Ted
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