From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jan Beulich , Konrad Rzeszutek Wilk , Vegard Nossum , Jens Axboe Subject: [PATCH 3.12 075/212] xen/blkback: fix reference counting Date: Mon, 2 Dec 2013 11:14:26 -0800 Message-Id: <20131202191256.206790368@linuxfoundation.org> In-Reply-To: <20131202191248.517975703@linuxfoundation.org> References: <20131202191248.517975703@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vegard Nossum commit ea5ec76d76da9279d12027c1828544c5ccbe7932 upstream. If the permission check fails, we drop a reference to the blkif without having taken it in the first place. The bug was introduced in commit 604c499cbbcc3d5fe5fb8d53306aa0fae1990109 (xen/blkback: Check device permissions before allowing OP_DISCARD). Cc: Jan Beulich Cc: Konrad Rzeszutek Wilk Signed-off-by: Vegard Nossum Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- drivers/block/xen-blkback/blkback.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/drivers/block/xen-blkback/blkback.c +++ b/drivers/block/xen-blkback/blkback.c @@ -887,6 +887,8 @@ static int dispatch_discard_io(struct xe unsigned long secure; struct phys_req preq; + xen_blkif_get(blkif); + preq.sector_number = req->u.discard.sector_number; preq.nr_sects = req->u.discard.nr_sectors; @@ -899,7 +901,6 @@ static int dispatch_discard_io(struct xe } blkif->st_ds_req++; - xen_blkif_get(blkif); secure = (blkif->vbd.discard_secure && (req->u.discard.flag & BLKIF_DISCARD_SECURE)) ? BLKDEV_DISCARD_SECURE : 0;