linux-kernel - Re: PING^7 (was Re: [PATCH v2 00/14] Corrections and customization of the SG

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Date:	Sat, 25 May 2013 09:21:10 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Christoph Hellwig <hch@...radead.org>
CC:	James Bottomley <James.Bottomley@...senPartnership.com>,
	Tejun Heo <tj@...nel.org>, Jens Axboe <axboe@...nel.dk>,
	lkml <linux-kernel@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>
Subject: Re: PING^7 (was Re: [PATCH v2 00/14] Corrections and customization
 of the SG_IO command whitelist (CVE-2012-4542))

Il 25/05/2013 09:11, Christoph Hellwig ha scritto:
> > Linus wanted to keep that for CAP_SYS_RAWIO.  We found two uses of SG_IO
> > on partitions: zfs-fuse used SYNCHRONIZE CACHE; some proprietary driver
> > used TEST UNIT READY.
> > 
> > Really, the solution is to make the bitmaps configurable in userspace.
> > It is no less secure than unpriv_sgio.  Then the kernel can be
> > configured at build-time to have either an MMC bitmap and a basic
> > whitelist of a dozen commands.  We can even avoid working around those
> > few conflicting opcodes; if you're paranoid you can just configure your
> > kernel right.
> 
> Keep it simple.  Allowing SG_IO for CAP_SYS_RAWIO probably is fine,
> allowing it for permissions only clearly isn't. All the per-command
> filetering is just complete bullshit and the kind of bloat that
> eventually will make Linux unmaintainable.

What I'm proposing is:

- by default, only allow INQUIRY / REPORT LUNS / TEST UNIT READY.  Keep
the old whitelist available for backwards-compatibility, configurable at
build-time.

- let CAP_SYS_ADMIN users set a different per-device whitelist.

Paolo
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