Messages in this thread | | | Date | Thu, 06 Sep 2012 08:31:33 +0200 | From | Paolo Bonzini <> | Subject | Re: [Ping^3] Re: [PATCH] sg_io: allow UNMAP and WRITE SAME without CAP_SYS_RAWIO |
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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.
> 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
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