* Re: [Xen-devel] [PATCH] xen/blkfront: avoid NULL blkfront_info dereference on device removal
[not found] <20181011162000.19191-1-vliaskovitis@suse.com>
@ 2018-10-11 16:34 ` Roger Pau Monné
2018-10-15 8:55 ` Vasilis Liaskovitis
0 siblings, 1 reply; 2+ messages in thread
From: Roger Pau Monné @ 2018-10-11 16:34 UTC (permalink / raw)
To: Vasilis Liaskovitis
Cc: xen-devel, linux-kernel, linux-block, jgross, axboe, konrad.wilk,
boris.ostrovsky
On Thu, Oct 11, 2018 at 06:20:00PM +0200, Vasilis Liaskovitis wrote:
> If a block device is hot-added when we are out of grants,
> gnttab_grant_foreign_access fails with -ENOSPC (log message "28
> granting access to ring page") in this code path:
>
> talk_to_blkback ->
> setup_blkring ->
> xenbus_grant_ring ->
> gnttab_grant_foreign_access
>
> and the failing path in talk_to_blkback sets the driver_data to NULL:
>
> destroy_blkring:
> blkif_free(info, 0);
>
> mutex_lock(&blkfront_mutex);
> free_info(info);
> mutex_unlock(&blkfront_mutex);
>
> dev_set_drvdata(&dev->dev, NULL);
>
> This results in a NULL pointer BUG when blkfront_remove and blkif_free
> try to access the failing device's NULL struct blkfront_info.
>
> Signed-off-by: Vasilis Liaskovitis <vliaskovitis@suse.com>
> ---
> drivers/block/xen-blkfront.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 429d20131c7e..92cc6cb6b078 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -2493,6 +2493,9 @@ static int blkfront_remove(struct xenbus_device *xbdev)
>
> dev_dbg(&xbdev->dev, "%s removed", xbdev->nodename);
>
> + if (!info)
> + goto out;
I don't see the point in adding the 'out' label. Can you just return 0
here?
Thanks, Roger.
^ permalink raw reply [flat|nested] 2+ messages in thread