From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756127Ab2APSsR (ORCPT ); Mon, 16 Jan 2012 13:48:17 -0500 Received: from cantor2.suse.de ([195.135.220.15]:42759 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756112Ab2APSsM (ORCPT ); Mon, 16 Jan 2012 13:48:12 -0500 X-Mailbox-Line: From gregkh@clark.kroah.org Mon Jan 16 10:45:16 2012 Message-Id: <20120116184516.054924109@clark.kroah.org> User-Agent: quilt/0.50-25.1 Date: Mon, 16 Jan 2012 10:44:30 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Brian Norris , Artem Bityutskiy , David Woodhouse Subject: [03/48] mtd: mtd_blkdevs: dont increase open count on error path In-Reply-To: <20120116184527.GA11972@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Brian Norris commit 342ff28f5a2e5aa3236617bd2bddf6c749677ef2 upstream. Some error paths in mtd_blkdevs were fixed in the following commit: commit 94735ec4044a6d318b83ad3c5794e931ed168d10 mtd: mtd_blkdevs: fix error path in blktrans_open But on these error paths, the block device's `dev->open' count is already incremented before we check for errors. This meant that, while the error path was handled correctly on the first time through blktrans_open(), the device is erroneously considered already open on the second time through. This problem can be seen, for instance, when a UBI volume is simultaneously mounted as a UBIFS partition and read through its corresponding gluebi mtdblockX device. This results in blktrans_open() passing its error checks (with `dev->open > 0') without actually having a handle on the device. Here's a summarized log of the actions and results with nandsim: # modprobe nandsim # modprobe mtdblock # modprobe gluebi # modprobe ubifs # ubiattach /dev/ubi_ctrl -m 0 ... # ubimkvol /dev/ubi0 -N test -s 16MiB ... # mount -t ubifs ubi0:test /mnt # ls /dev/mtdblock* /dev/mtdblock0 /dev/mtdblock1 # cat /dev/mtdblock1 > /dev/null cat: can't open '/dev/mtdblock4': Device or resource busy # cat /dev/mtdblock1 > /dev/null CPU 0 Unable to handle kernel paging request at virtual address fffffff0, epc == 8031536c, ra == 8031f280 Oops[#1]: ... Call Trace: [<8031536c>] ubi_leb_read+0x14/0x164 [<8031f280>] gluebi_read+0xf0/0x148 [<802edba8>] mtdblock_readsect+0x64/0x198 [<802ecfe4>] mtd_blktrans_thread+0x330/0x3f4 [<8005be98>] kthread+0x88/0x90 [<8000bc04>] kernel_thread_helper+0x10/0x18 Signed-off-by: Brian Norris Signed-off-by: Artem Bityutskiy Signed-off-by: David Woodhouse Signed-off-by: Greg Kroah-Hartman --- drivers/mtd/mtd_blkdevs.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/drivers/mtd/mtd_blkdevs.c +++ b/drivers/mtd/mtd_blkdevs.c @@ -215,7 +215,7 @@ static int blktrans_open(struct block_de mutex_lock(&dev->lock); - if (dev->open++) + if (dev->open) goto unlock; kref_get(&dev->ref); @@ -235,6 +235,7 @@ static int blktrans_open(struct block_de goto error_release; unlock: + dev->open++; mutex_unlock(&dev->lock); blktrans_dev_put(dev); return ret;