Messages in this thread | | | Date | Tue, 14 Aug 2012 16:00:32 -0400 | From | Vivek Goyal <> | Subject | Re: [PATCH v3 3/6] floppy: avoid leaking extra reference to queue on do_floppy_init error handling |
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On Tue, Aug 14, 2012 at 04:20:39AM +0100, Ben Hutchings wrote: > On Mon, 2012-08-13 at 15:16 -0300, Herton Ronaldo Krzesinski wrote: > > After commit 3f9a5aa ("floppy: Cleanup disk->queue before caling > > put_disk() if add_disk() was never called"), if something fails in the > > add_disk loop, we unconditionally set disks[dr]->queue to NULL. But > > that's wrong, since we may have succesfully done an add_disk on some of > > the drives previously in the loop, and in this case we would end up with > > an extra reference to the disks[dr]->queue. > > > > Add a new global array to mark "registered" disks, and use that to check > > if we did an add_disk on one of the disks already. Using an array to > > track added disks also will help to simplify/cleanup code later, as > > suggested by Vivek Goyal. > [...] > > It's totally ridiculous that a driver should have to do this. Any > registered disk should have the GENHD_FL_UP flag set... so why can't > genhd check it? It doesn't look like floppy is the only driver affected > by this problem, either. So I suggest the following general fix > (untested): > > --- > Subject: genhd: Make put_disk() safe for disks that have not been registered > > Since commit 9f53d2f ('block: fix __blkdev_get and add_disk race > condition'), add_disk() adds a reference to disk->queue, which is then > dropped by disk_release(). But if a disk is destroyed without being > registered through add_disk() (or if add_disk() fails at the first > hurdle) then we have a reference imbalance. > > Use the GENHD_FL_UP flag to tell whether this extra reference has been > added. Remove the incomplete workaround from the floppy driver. >
Checking for GENHD_FL_UP to represent whether we took a reference on the disk->queue or not sounds reasonable.
Thanks Vivek
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