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Open Source and information security mailing list archives
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Date: Thu, 01 Nov 2007 10:51:07 -0400 From: Ric Wheeler <ric@....com> To: Pavel Machek <pavel@....cz> CC: Mike Waychison <mikew@...gle.com>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, Linux Kernel <linux-kernel@...r.kernel.org> Subject: Re: [patch 1/1] Drop CAP_SYS_RAWIO requirement for FIBMAP Pavel Machek wrote: > Hi! > >> Remove the need for having CAP_SYS_RAWIO when doing a FIBMAP call on an open file descriptor. >> >> It would be nice to allow users to have permission to see where their data is landing on disk, and there really isn't a good reason to keep them from getting at this information. > > I believe it is to prevent users from intentionally creating extremely > fragmented files... > > You can read 60MB in a second, but fragmented 60MB file could take > 10msec * 60MB/4KB = 150 seconds. That's factor 150 slowdown... > > ...but I agree that SYS_RAWIO may be wrong capability to cover this. > > Pavel I don't see how restricting FIBMAP use helps prevent fragmentation since FIBMAP just allows you to see what damage was already done. You can create nicely fragmented files simply by having multiple threads writing concurrently to one or more files in the same directory (depending on the file system, allocation policy, etc). ric - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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