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SubjectRe: [PATCH v2] xen/blkfront: avoid NULL blkfront_info dereference on device removal
On Mon, Oct 15, 2018 at 03:25:08PM +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>

Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks.

I guess this is a candidate for backporting?

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