|To:||David Chinner <dgc@xxxxxxx>|
|Subject:||Re: [RFC] add FIEMAP ioctl to efficiently map file allocation|
|From:||Anton Altaparmakov <aia21@xxxxxxxxx>|
|Date:||Tue, 1 May 2007 19:37:20 +0100|
|Cc:||linux-ext4@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, hch@xxxxxxxxxxxxx|
|References:||<20070412110550.GM5967@xxxxxxxxxxxxxxxxxxxx> <20070416112252.GJ48531920@xxxxxxxxxxxxxxxxx> <20070419002139.GK5967@xxxxxxxxxxxxxxxxxxxx> <20070419015426.GM48531920@xxxxxxxxxxxxxxxxx> <20070430224401.GX5967@xxxxxxxxxxxxxxxxxxxx> <20070501042254.GD77450368@xxxxxxxxxxxxxxxxx>|
On 1 May 2007, at 05:22, David Chinner wrote:
On Mon, Apr 30, 2007 at 04:44:01PM -0600, Andreas Dilger wrote:The FIBMAP ioctl is for privileged usersonly, and I wonder if FIEMAP should be the same, or at least disallow mapping files that the user can't access especially with FLAG_SYNC and/orFLAG_HSM_READ.I see little reason for restricting FI[BE]MAP to privileged users - anyone should be able to determine if files they have permission to access are fragmented.
Allowing anyone to run FI[BE]MAP creates potential for DOS-ing the machine. Perhaps for non-privileged users FIEMAP has to be read- only? As soon as any of the FLAG_* flags come into play you make it privileged. For example fancy any user being able to fill up your file system by calling FIEMAP with FLAG_HSM_READ on all files recursively? This should certainly not be simply dismissed as a non- issue without thinking about it first...
Best regards, Anton -- Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @) Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK Linux NTFS maintainer, http://www.linux-ntfs.org/
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