linux-kernel - Re: [PATCH stable 3/4] block: fail SCSI passthrough ioctls on partition devices

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Message-ID: <1326902676.3271.10.camel@deadeye>
Date:	Wed, 18 Jan 2012 16:04:36 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	stable@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Petr Matousek <pmatouse@...hat.com>,
	linux-scsi@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
	James Bottomley <JBottomley@...allels.com>
Subject: Re: [PATCH stable 3/4] block: fail SCSI passthrough ioctls on
 partition devices

On Wed, 2012-01-18 at 10:00 +0100, Paolo Bonzini wrote:
> On 01/18/2012 05:47 AM, Ben Hutchings wrote:
> > >     Changes with respect to 3.3: return -ENOTTY from scsi_verify_blk_ioctl
> > >     and -ENOIOCTLCMD from sd_compat_ioctl. ]
> >
> > But in 2.6.32, compat_sys_ioctl will end up returning EINVAL rather than
> > ENOTTY for an unhandled ioctl number.
> 
> No, it won't.  The ioctl will percolate up the non-compat path and then 
> sd_ioctl will return ENOTTY.

Ah, yes.

> > Also, since we're denying ioctls
> > for security reasons rather than because we don't know how to handle
> > them, I don't think there's any harm in doing this.
> 
> There is harm.  You'll be blacklisting also the standard block device 
> ioctls, and those won't work on 32-on-64 anymore.  A system with 32-bit 
> userland will likely not boot anymore.

It does (yes, I tested that myself now).  The standard block device
ioctls are handled without calling the driver's compat_ioctl.

> This is also somewhat exchanged in my original exchange with Linus.

Anyway, I agree that it is not necessary to differ from mainline here.

Ben.

-- 
Ben Hutchings
When in doubt, use brute force. - Ken Thompson


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