linux-kernel - [ 02/70] floppy: Cleanup disk->queue before caling put_disk() if add

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Date:	Tue, 07 Aug 2012 04:27:57 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Vivek Goyal <vgoyal@...hat.com>,
	Dirk Gouders <gouders@...bocholt.fh-gelsenkirchen.de>,
	Tejun Heo <tj@...nel.org>, Jens Axboe <axboe@...nel.dk>
Subject: [ 02/70] floppy: Cleanup disk->queue before caling put_disk() if add_disk()
 was never called

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vivek Goyal <vgoyal@...hat.com>

commit 3f9a5aabd0a9fe0e0cd308506f48963d79169aa7 upstream.

add_disk() takes gendisk reference on request queue. If driver failed during
initialization and never called add_disk() then that extra reference is not
taken. That reference is put in put_disk(). floppy driver allocates the
disk, allocates queue, sets disk->queue and then relizes that floppy
controller is not present. It tries to tear down everything and tries to
put a reference down in put_disk() which was never taken.

In such error cases cleanup disk->queue before calling put_disk() so that
we never try to put down a reference which was never taken in first place.

Reported-and-tested-by: Suresh Jayaraman <sjayaraman@...e.com>
Tested-by: Dirk Gouders <gouders@...bocholt.fh-gelsenkirchen.de>
Signed-off-by: Vivek Goyal <vgoyal@...hat.com>
Acked-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/block/floppy.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 510fb10..401ba78 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -4368,8 +4368,14 @@ out_unreg_blkdev:
 out_put_disk:
 	while (dr--) {
 		del_timer_sync(&motor_off_timer[dr]);
-		if (disks[dr]->queue)
+		if (disks[dr]->queue) {
 			blk_cleanup_queue(disks[dr]->queue);
+			/*
+			 * put_disk() is not paired with add_disk() and
+			 * will put queue reference one extra time. fix it.
+			 */
+			disks[dr]->queue = NULL;
+		}
 		put_disk(disks[dr]);
 	}
 	return err;


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