On Tue, 2011-05-03 at 11:27 -0600, Jim Schutt wrote:
> James Bottomley wrote:
> > On Tue, 2011-05-03 at 10:53 -0600, Jim Schutt wrote:
> >> Please let me know if what further information you need, or if there is
> >> anything I can do, to help resolve this.
> >
> > I think this is the fix (already in rc-fixes):
> >
> > James
> >
> > ---
> > From 3e85ea868dbd60a84240be5c1eebc36841b9c568 Mon Sep 17 00:00:00 2001
> > From: James Bottomley <James.Bottomley@xxxxxxx>
> > Date: Sun, 1 May 2011 09:42:07 -0500
> > Subject: [PATCH] [SCSI] fix oops in scsi_run_queue()
> >
> > The recent commit closing the race window in device teardown:
> >
> > commit 86cbfb5607d4b81b1a993ff689bbd2addd5d3a9b
> > Author: James Bottomley <James.Bottomley@xxxxxxx>
> > Date: Fri Apr 22 10:39:59 2011 -0500
> >
> > [SCSI] put stricter guards on queue dead checks
> >
> > is causing a potential NULL deref in scsi_run_queue() because the
> > q->queuedata may already be NULL by the time this function is called.
> > Since we shouldn't be running a queue that is being torn down, simply
> > add a NULL check in scsi_run_queue() to forestall this.
> >
> > Signed-off-by: James Bottomley <James.Bottomley@xxxxxxx>
> >
> > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> > index e9901b8..03979f4 100644
> > --- a/drivers/scsi/scsi_lib.c
> > +++ b/drivers/scsi/scsi_lib.c
> > @@ -404,6 +404,10 @@ static void scsi_run_queue(struct request_queue *q)
> > LIST_HEAD(starved_list);
> > unsigned long flags;
> >
> > + /* if the device is dead, sdev will be NULL, so no queue to run */
> > + if (!sdev)
> > + return;
> > +
> > if (scsi_target(sdev)->single_lun)
> > scsi_single_lun_run(sdev);
> >
>
> Hmmm, with the above added, I still get BUGs. Here's an
> example:
>
> [ 17.142931] BUG: unable to handle kernel NULL pointer dereference at (null)
> [ 17.143002] IP: [<ffffffffa01cf8c5>] scsi_run_queue+0x24/0xec [scsi_mod]
Ooh, compiler optimisation, I think; try this instead
James
---
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index e9901b8..0bac91e 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -400,10 +400,15 @@ static inline int scsi_host_is_busy(struct Scsi_Host *shost)
static void scsi_run_queue(struct request_queue *q)
{
struct scsi_device *sdev = q->queuedata;
- struct Scsi_Host *shost = sdev->host;
+ struct Scsi_Host *shost;
LIST_HEAD(starved_list);
unsigned long flags;
+ /* if the device is dead, sdev will be NULL, so no queue to run */
+ if (!sdev)
+ return;
+
+ shost = sdev->host;
if (scsi_target(sdev)->single_lun)
scsi_single_lun_run(sdev);
--
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