Messages in this thread | | | Date | Thu, 06 Sep 2012 07:31:45 -0400 | From | Ric Wheeler <> | Subject | Re: [Ping^3] Re: [PATCH] sg_io: allow UNMAP and WRITE SAME without CAP_SYS_RAWIO |
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On 09/06/2012 02:31 AM, Paolo Bonzini wrote: > Il 05/09/2012 22:18, Ric Wheeler ha scritto: >> Hi Paolo, >> >> Both of these commands are destructive. WRITE_SAME (if done without the >> discard bits set) can also take a very long time to be destructive and >> tie up the storage. > FORMAT_UNIT has the same characteristics and yet it is allowed (btw, I > don't think WRITE SAME slowness is limited to the case where a real > write is requested; discarding can be just as slow). > > Also, the two new commands are anyway restricted to programs that have > write access to the disk. If you have read-only access, you won't be > able to issue any destructive command (there is one exception, START > STOP UNIT is allowed even with read-only capability and is somewhat > destructive). > > Honestly, the only reason why these two commands weren't included, is > that the current whitelist is heavily tailored towards CD/DVD burning.
Hi Paolo,
I assume that FORMAT_UNIT is for CD/DVD needs - not sure what a S-ATA disk would do with that. If it is destructive, we should probably think about how to make it more secure and see how many applications we would break.
> >> I think that restricting them to CAP_SYS_RAWIO seems reasonable - better >> to vet and give the appropriate apps the needed capability than to >> widely open up the safety check? > CAP_SYS_RAWIO is so wide in its scope, that anything that requires it is > insecure. > > Paolo
I don't see allowing anyone who can open the device to zero the data as better though :)
Ric
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