linux-kernel - Re: [PATCH] ide-cd: prevent null pointer deref via cdrom_newpc

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Date:	Sat, 20 Jun 2009 12:27:31 +0200
From:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
To:	Borislav Petkov <petkovbb@...glemail.com>
Cc:	Rainer Weikusat <rweikusat@...gmbh.com>,
	linux-kernel@...r.kernel.org,
	Linux IDE mailing list <linux-ide@...r.kernel.org>,
	bruinjm@...all.nl
Subject: Re: [PATCH] ide-cd: prevent null pointer deref via cdrom_newpc_intr

On Thursday 18 June 2009 18:06:34 Borislav Petkov wrote:
> Hi,
> 
> On Thu, Jun 18, 2009 at 5:04 PM, Rainer Weikusat<rweikusat@...gmbh.com> wrote:
> > From: Rainer Weikusat <rweikusat@...gmbh.com>
> >
> > With 2.6.30, the error handling code in cdrom_newpc_intr was changed
> > to deal with partial request failures by normally completing the 'good'
> > parts of a request and only 'error' the last (and presumably,
> > incompletely transferred) bio associated with a particular
> > request. In order to do this, ide_complete_rq is called over
> > ide_cd_error_cmd() to partially complete the rq. The block layer
> > does partial completion only for requests with bio's and if the
> > rq doesn't have one (eg 'GPCMD_READ_DISC_INFO') the request is
> > completed as a whole and the drive->hwif->rq pointer set to NULL
> > afterwards. When calling ide_complete_rq again to report
> > the error, this null pointer is derefenced, resulting in a kernel
> > crash.

Rainer, thanks for fixing this bug (with a lot of extra points for
the detailed explanation).

> @Bart: please apply.

applied [I kept the above patch description]
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