linux-ext4 - Re: [PATCH] ext4: Fix offset overflow on 32-bit archs in ext4_iomap

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Date:   Thu, 22 Mar 2018 11:49:35 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-ext4@...r.kernel.org, Jiri Slaby <jslaby@...e.cz>
Subject: Re: [PATCH] ext4: Fix offset overflow on 32-bit archs in
 ext4_iomap_begin()

On Tue, Feb 20, 2018 at 06:23:07PM +0100, Jan Kara wrote:
> From: Jiri Slaby <jslaby@...e.cz>
> 
> ext4_iomap_begin() has a bug where offset returned in the iomap
> structure will be truncated to unsigned long size. On 64-bit
> architectures this is fine but on 32-bit architectures obviously not.
> Not many places actually use the offset stored in the iomap structure
> but one of visible failures is in SEEK_HOLE / SEEK_DATA implementation.
> If we create a file like:
> 
> dd if=/dev/urandom of=file bs=1k seek=8m count=1
> 
> then
> 
> lseek64("file", 0x100000000ULL, SEEK_DATA)
> 
> wrongly returns 0x100000000 on unfixed kernel while it should return
> 0x200000000. Avoid the overflow by proper type cast.
> 
> Fixes: 545052e9e35a ("ext4: Switch to iomap for SEEK_HOLE / SEEK_DATA")
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> Signed-off-by: Jan Kara <jack@...e.cz>

Thanks, applied.

					- Ted