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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