Commit 4c49ff3f authored Jun 01, 2011 by Tejun Heo Committed by Jens Axboe Jun 01, 2011

block: blkdev_get() should access ->bd_disk only after success



d4dc210f (block: don't block events on excl write for non-optical
devices) added dereferencing of bdev->bd_disk to test
GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE; however, bdev->bd_disk can be
%NULL if open failed which can lead to an oops.

Test the flag after testing open was successful, not before.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: David Miller <davem@davemloft.net>
Tested-by: David Miller <davem@davemloft.net>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

parent 4495a7d4

fs/block_dev.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1272,8 +1272,8 @@ int blkdev_get(struct block_device bdev, fmode_t mode, void holder)
		* individual writeable reference is too fragile given the
		* way @mode is used in blkdev_get/put().
		*/
		if ((disk->flags & GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE) &&
		!res && (mode & FMODE_WRITE) && !bdev->bd_write_holder) {
		if (!res && (mode & FMODE_WRITE) && !bdev->bd_write_holder &&
		(disk->flags & GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE)) {
		bdev->bd_write_holder = true;
		disk_block_events(disk);
		}