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SubjectRe: [PATCH v2 0/3] block: add queue-private command filter, editable via sysfs
Il 25/09/2012 17:30, Paolo Bonzini ha scritto:
> The set of use cases for SG_IO is quite variable that no single filter can
> accomodate all of them. The current filter is tailored very much to
> CD burning, and includes many MMC-specific commands that may have
> other meanings in different standards. Someone may want to remove
> those commands; at the same time, people that trust their users may
> want to add persistent reservations, trim/discard, or even access to
> vendor-specific commands.
>
> Filters used to be mutable via sysfs, but the implementation was
> never enabled. Add it back, and let the admin set this up per device.
>
> A simple bitmap does not let you do things like enabling command A with
> option B on a specific device for a certain block range. However, the
> question is really whether this is needed---in fact, neither of the known
> uses for the filtering need it.
>
> In one use case, the administrator then needs the ability to configure
> devices easily, for example to be much more restrictive on non-MMC
> devices. It must be done with the same tools it uses for other aspects
> of the policy---which will be a combination of DAC (Unix permissions and
> ACLs) and sysfs. Different SCSI standards may give different meanings
> for the same byte value, but a simple bitmap is enough for this.
>
> In the virtualization case, the problem is really that you want to
> pass through everything or almost everything, while still running as
> confined as possible (i.e. CAP_SYS_RAWIO is not a choice). But in this
> case a more complex filtering can be done just as easily in userspace,
> in the virtual machine monitor. While the userspace filter can be
> subverted if the guest can escape the QEMU jail, the bitmap still lets
> you block some commands at the kernel level if really necessary.
>
> One alternative is a ioctl to disable the filter altogether, to be
> used together with SCM_RIGHTS file descriptor passing. This works in
> the virtualization case but not for policy decisions. So this patch
> series provides the sysfs knob. It is a tweaked revert of commit 018e044
> (block: get rid of queue-private command filter, 2009-06-26).
>
> Please review!
>
> Paolo
>
> v1->v2: add OOM and capability checks
>
> Paolo Bonzini (3):
> block: add back queue-private command filter
> scsi: create an all-zero filter for scanners
> block: add back command filter modification via sysfs
>
> Documentation/block/queue-sysfs.txt | 16 +++++
> block/Kconfig | 10 +++
> block/blk-sysfs.c | 43 +++++++++++++
> block/bsg.c | 2 +-
> block/scsi_ioctl.c | 117 +++++++++++++++++++++++++++++++----
> drivers/scsi/scsi_scan.c | 6 ++-
> drivers/scsi/sg.c | 7 +-
> include/linux/blkdev.h | 31 +++++++++-
> 8 files changed, 213 insertions(+), 19 deletions(-)
>
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>

Ping?

Tejun, Jens, anyone else, any hope that this gets in 3.7?

Paolo


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