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Date: Tue, 03 Mar 2009 13:59:06 -0800
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: Kris Shannon <kris@...nnon.id.au>
CC: Linux Kernel List <linux-kernel@...r.kernel.org>,
Xen-devel <xen-devel@...ts.xensource.com>,
Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [PATCH] Fix kernel NULL pointer dereference in xen-blkfront
Kris Shannon wrote:
> When booting Xen Dom0 on a pre-release 3.2.1 hypervisor the system Oopses on a
> "Unable to handle kernel NULL pointer dereference" in xenwatch.
>
> From the backtrace it looks like backend_changed is calling bdget_disk
> with a NULL pointer. Checking for NULL and returning ENODEV instead
> allows the kernel to boot.
>
Thanks, applied. (BTW, please cc: me and xen-devel for Xen-related
reports.)
Jens: could you pull this; I think this is probably -rc material. This
crash just started happening, so I guess its a side-effect of some core
kernel change.
The following changes since commit c7241227f61ca6606a7fa3555391360d92bd8d9b:
Jens Axboe (1):
xen/blkfront: use blk_rq_map_sg to generate ring entries
are available in the git repository at:
git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git xen/frontend/blkfront
Kris Shannon (1):
Fix kernel NULL pointer dereference in xen-blkfront
drivers/block/xen-blkfront.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
Thanks,
J
> ---
> drivers/block/xen-blkfront.c | 2 ++
> 1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index f2fff5799ddf0fe1b41909b64d606d..3e2ab6d53adaeb70efa12f0a1f33bb 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -905,6 +905,8 @@ static void backend_changed(struct xenbus_device *dev,
> break;
>
> case XenbusStateClosing:
> + if (info->gd == NULL)
> + xenbus_dev_fatal(dev, -ENODEV, "gd is NULL");
> bd = bdget_disk(info->gd, 0);
> if (bd == NULL)
> xenbus_dev_fatal(dev, -ENODEV, "bdget failed");
>
--
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