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Date: Thu, 26 Jan 2012 10:04:20 -0500 From: Vivek Goyal <vgoyal@...hat.com> To: Suresh Jayaraman <sjayaraman@...e.com> Cc: LKML <linux-kernel@...r.kernel.org>, Tejun Heo <tj@...nel.org>, Jens Axboe <axboe@...nel.dk>, Dirk Gouders <gouders@...bocholt.fh-gelsenkirchen.de> Subject: Re: Slab corruption in floppy driver module On Tue, Jan 24, 2012 at 05:31:53PM -0500, Vivek Goyal wrote: [..] > > Reverting f992ae80 makes the oops and the slab corruption messages disappear. > > The "no floppy controllers found" message was found in the dmesg. > > I am wondering if extra queue reference for gendisk should be taken by driver > and not by add_disk(). Why? Because disk->queue association is setup by > driver and not by add_disk(). That way even if we don't call, add_disk(), > we should be fine. Well, changing above assumption will require lots of drivers to be changed. So probably an easier fix would be to clear disk->queue before calling put_disk() if we never called add_disk(). Suresh, does following patch help? Thanks Vivek floppy: Cleanup disk->queue before caling put_disk() if add_disk() was never called 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-by: Suresh Jayaraman <sjayaraman@...e.com> Signed-off-by: Vivek Goyal <vgoyal@...hat.com> --- drivers/block/floppy.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) Index: linux-2.6/drivers/block/floppy.c =================================================================== --- linux-2.6.orig/drivers/block/floppy.c 2012-01-15 09:49:14.000000000 -0500 +++ linux-2.6/drivers/block/floppy.c 2012-01-26 09:51:24.389205883 -0500 @@ -4368,8 +4368,21 @@ 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); + /* + * The request queue reference we took at device + * creation time has been put by above + * blk_cleanup_queue(). We have not called add_disk() + * yet and due to failure calling put_disk(). Put disk + * will try to put a reference to disk->queue which is + * taken in add_disk(). As we have not taken that + * extra reference, putting extra reference down + * will try to access already freed queue. Clear + * disk->queue before calling put_disk(). + */ + disks[dr]->queue = NULL; + } put_disk(disks[dr]); } return err; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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