Messages in this thread | | | From | Dirk Gouders <> | Subject | Re: Slab corruption in floppy driver module | Date | Thu, 26 Jan 2012 22:48:57 +0100 |
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Vivek Goyal <vgoyal@redhat.com> writes:
> On Thu, Jan 26, 2012 at 10:05:32AM -0800, Tejun Heo wrote: >> Hello, >> >> On Thu, Jan 26, 2012 at 10:04:20AM -0500, Vivek Goyal wrote: >> > 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; >> >> Yeah, this looks correct to me. It might be better to tone down the >> comment a bit tho. Wouldn't it be sufficient to say put_disk() isn't >> paired with add_disk() and will put one extra time? > > Sure. Toned down the comment as suggested. Here is the new patch. > > 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@suse.com> > Tested-by: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de> > Signed-off-by: Vivek Goyal <vgoyal@redhat.com> > --- > drivers/block/floppy.c | 8 +++++++- > 1 file changed, 7 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 14:35:14.662374464 -0500 > @@ -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;
Probably a rare and uncommon one but it seems that the reloading case on a machine that has a floppy controller is a different problem. To be sure I tested the patch on a machine that has a floppy controller and when unloading and reloading the floppy module the log messages that I attached to a mail earlier in this thread are still generated.
Dirk
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