Re: [Ping^3] Re: [PATCH] sg_io: allow UNMAP and WRITE SAME withoutCAP_SYS_RAWIO

[Ric Wheeler]

On 09/05/2012 10:41 AM, Paolo Bonzini wrote:
> Il 28/08/2012 13:04, Paolo Bonzini ha scritto:
> > Il 01/08/2012 17:53, Paolo Bonzini ha scritto:
> > > Il 20/07/2012 18:30, Paolo Bonzini ha scritto:
> > > > These commands cannot be issued right now without giving CAP_SYS_RAWIO to
> > > > the process who wishes to send them.  These commands can be useful also to
> > > > non-privileged programs who have access to the block devices.  For example
> > > > a virtual machine monitor needs them to forward trim/discard to host disks.
> > > >
> > > > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > > > ---
> > > >   block/scsi_ioctl.c |    3 ++
> > > >   1 files changed, 3 insertions(+), 0 deletions(-)
> > > >
> > > > diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
> > > > index 260fa80..dd71f18 100644
> > > > --- a/block/scsi_ioctl.c
> > > > +++ b/block/scsi_ioctl.c
> > > > @@ -168,13 +168,16 @@ static void blk_set_cmd_filter_defaults(struct blk_cmd_filter *filter)
> > > >   	/* Basic writing commands */
> > > >   	__set_bit(WRITE_6, filter->write_ok);
> > > >   	__set_bit(WRITE_10, filter->write_ok);
> > > > +	__set_bit(WRITE_SAME, filter->write_ok);
> > > >   	__set_bit(WRITE_VERIFY, filter->write_ok);
> > > >   	__set_bit(WRITE_12, filter->write_ok);
> > > >   	__set_bit(WRITE_VERIFY_12, filter->write_ok);
> > > >   	__set_bit(WRITE_16, filter->write_ok);
> > > > +	__set_bit(WRITE_SAME_16, filter->write_ok);
> > > >   	__set_bit(WRITE_LONG, filter->write_ok);
> > > >   	__set_bit(WRITE_LONG_2, filter->write_ok);
> > > >   	__set_bit(ERASE, filter->write_ok);
> > > > +	__set_bit(UNMAP, filter->write_ok);
> > > >   	__set_bit(GPCMD_MODE_SELECT_10, filter->write_ok);
> > > >   	__set_bit(MODE_SELECT, filter->write_ok);
> > > >   	__set_bit(LOG_SELECT, filter->write_ok);
> > > Jens,
> > >
> > > can this go in 3.6 as well?
> > Another ping...
> Ping & adding some more folks hoping to get a Reviewed-by or to be
> screamed at.
>
> Paolo

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.

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?

thanks!

Ric


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