linux-kernel - Re: setting up CDB filters in udev (was Re: [PATCH v2 0/3] block: add queue-private command filter, editable via sysfs)

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Message-ID: <20121102201824.41b2516d@pyramind.ukuu.org.uk>
Date:	Fri, 2 Nov 2012 20:18:24 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Tejun Heo <tj@...nel.org>
Cc:	Paolo Bonzini <pbonzini@...hat.com>,
	Ric Wheeler <rwheeler@...hat.com>,
	Petr Matousek <pmatouse@...hat.com>,
	Kay Sievers <kay@...hat.com>, Jens Axboe <axboe@...nel.dk>,
	linux-kernel@...r.kernel.org,
	"James E.J. Bottomley" <James.Bottomley@...senPartnership.com>
Subject: Re: setting up CDB filters in udev (was Re: [PATCH v2 0/3] block:
 add queue-private command filter, editable via sysfs)

>  * Devices are given standard filter matching the device class.  Any
>    !CAP_SYS_RAWIO user can only issue commands allowed by the filter.
> 
>  * CAP_SYS_RAWIO can issue an ioctl to disable the filter all
>    accessors of the fd and transfer it.
> 
> That should be enough, no?

No 

a - there are lots of cases you want to allow only a subset of commands.

b - if you are using a BPF filter which is the obvious way to do it then
the flexibility comes for free without any extra complexity as the kernel
provides a generic implementation, and even a JIT for complex cases.

Alan
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