floppy: fix use-after-free in module load failure path

Commit 488211844e0c ("floppy: switch to one queue per drive instead of
sharing a queue") introduced a use-after-free.  We do "put_disk()" on
the disk device _before_ we then clean up the queue associated with that
disk.

Move the put_disk() down to avoid dereferencing a free'd data structure.

Cc: Jens Axboe <jaxboe@fusionio.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Reported-and-tested-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 767107c..8f19b38 100644 (file)
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -4363,9 +4363,9 @@ out_unreg_blkdev:
 out_put_disk:
        while (dr--) {
                del_timer(&motor_off_timer[dr]);
-               put_disk(disks[dr]);
                if (disks[dr]->queue)
                        blk_cleanup_queue(disks[dr]->queue);
+               put_disk(disks[dr]);
        }
        return err;
 }