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

PATCH Applied Tejun Heo 2 participants 2 messages May 31, 2011 – Jun 1, 2011 VFS

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Tejun Heo

author

2011-05-31 23:56 UTC #0 lore raw

PATCH 1/1 block: blkdev_get() should acess ->bd_disk only after success

d4dc210f69 (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 <[email protected]>

Reported-by David Miller <[email protected]>

Tested-by David Miller <[email protected]>

Cc [email protected]

---
 fs/block_dev.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

fs/block_dev.c +2 -2

index 1f2b199..1a2421f 100644
@@ -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);
 		}

Jens Axboe

Applied

2011-06-01 06:29 UTC #1 lore raw

Quoted 6 lines · Tejun Heo

d4dc210f69 (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.

Thanks, applied.

Signature · 1 line

Jens Axboe