Messages in this thread Patch in this message | | | From | Vasilis Liaskovitis <> | Subject | [PATCH v2] xen/blkfront: avoid NULL blkfront_info dereference on device removal | Date | Mon, 15 Oct 2018 15:25:08 +0200 |
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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 | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 429d20131c7e..8871bf4c8a2e 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) + return 0; + blkif_free(info, 0); mutex_lock(&info->mutex); -- 2.19.0
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