From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qw0-f49.google.com ([209.85.216.49]) by merlin.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1RNYyi-0005qg-Iw for linux-mtd@lists.infradead.org; Mon, 07 Nov 2011 23:51:49 +0000 Received: by qap15 with SMTP id 15so4687303qap.36 for ; Mon, 07 Nov 2011 15:51:46 -0800 (PST) From: Brian Norris To: Artem Bityutskiy Subject: [PATCH] mtd: mtd_blkdevs: don't increase 'open' count on error path Date: Mon, 7 Nov 2011 15:51:05 -0800 Message-Id: <1320709865-21903-1-git-send-email-computersforpeace@gmail.com> Cc: Kevin Cernekee , Brian Norris , linux-mtd@lists.infradead.org, David Woodhouse List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 Cc: stable@kernel.org [3.0+] Signed-off-by: Brian Norris --- drivers/mtd/mtd_blkdevs.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c index ed8b5e7..424ca5f 100644 --- a/drivers/mtd/mtd_blkdevs.c +++ b/drivers/mtd/mtd_blkdevs.c @@ -215,7 +215,7 @@ static int blktrans_open(struct block_device *bdev, fmode_t mode) 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_device *bdev, fmode_t mode) goto error_release; unlock: + dev->open++; mutex_unlock(&dev->lock); blktrans_dev_put(dev); return ret; -- 1.7.5.4