From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:59508 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390832AbeKLIYO (ORCPT ); Mon, 12 Nov 2018 03:24:14 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vasilis Liaskovitis , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= , Konrad Rzeszutek Wilk , Jens Axboe Subject: [PATCH 4.9 078/141] xen/blkfront: avoid NULL blkfront_info dereference on device removal Date: Sun, 11 Nov 2018 14:25:37 -0800 Message-Id: <20181111221638.811805265@linuxfoundation.org> In-Reply-To: <20181111221627.853046496@linuxfoundation.org> References: <20181111221627.853046496@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vasilis Liaskovitis commit f92898e7f32e3533bfd95be174044bc349d416ca upstream. 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. Cc: stable@vger.kernel.org # 4.5 and later Signed-off-by: Vasilis Liaskovitis Reviewed-by: Roger Pau Monné Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- drivers/block/xen-blkfront.c | 3 +++ 1 file changed, 3 insertions(+) --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -2524,6 +2524,9 @@ static int blkfront_remove(struct xenbus dev_dbg(&xbdev->dev, "%s removed", xbdev->nodename); + if (!info) + return 0; + blkif_free(info, 0); mutex_lock(&info->mutex);