3.16.51-rc1 review patch. If anyone has any objections, please let me know.
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From: Bart Van Assche bart.vanassche@wdc.com
commit 7277cc67b3916eed47558c64f9c9c0de00a35cda upstream.
Since put_disk() triggers a disk_release() call and since that last function calls blk_put_queue() if disk->queue != NULL, clear the disk->queue pointer before calling put_disk(). This avoids that unloading the skd kernel module triggers the following use-after-free:
WARNING: CPU: 8 PID: 297 at lib/refcount.c:128 refcount_sub_and_test+0x70/0x80 refcount_t: underflow; use-after-free. CPU: 8 PID: 297 Comm: kworker/8:1 Not tainted 4.11.10-300.fc26.x86_64 #1 Workqueue: events work_for_cpu_fn Call Trace: dump_stack+0x63/0x84 __warn+0xcb/0xf0 warn_slowpath_fmt+0x5a/0x80 refcount_sub_and_test+0x70/0x80 refcount_dec_and_test+0x11/0x20 kobject_put+0x1f/0x50 blk_put_queue+0x15/0x20 disk_release+0xae/0xf0 device_release+0x32/0x90 kobject_release+0x67/0x170 kobject_put+0x2b/0x50 put_disk+0x17/0x20 skd_destruct+0x5c/0x890 [skd] skd_pci_probe+0x124d/0x13a0 [skd] local_pci_probe+0x42/0xa0 work_for_cpu_fn+0x14/0x20 process_one_work+0x19e/0x470 worker_thread+0x1dc/0x4a0 kthread+0x125/0x140 ret_from_fork+0x25/0x30
Signed-off-by: Bart Van Assche bart.vanassche@wdc.com Cc: Christoph Hellwig hch@lst.de Cc: Hannes Reinecke hare@suse.de Cc: Johannes Thumshirn jthumshirn@suse.de Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/block/skd_main.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-)
--- a/drivers/block/skd_main.c +++ b/drivers/block/skd_main.c @@ -4685,15 +4685,16 @@ static void skd_free_disk(struct skd_dev { struct gendisk *disk = skdev->disk;
- if (disk != NULL) { - struct request_queue *q = disk->queue; + if (disk && (disk->flags & GENHD_FL_UP)) + del_gendisk(disk);
- if (disk->flags & GENHD_FL_UP) - del_gendisk(disk); - if (q) - blk_cleanup_queue(q); - put_disk(disk); + if (skdev->queue) { + blk_cleanup_queue(skdev->queue); + skdev->queue = NULL; + disk->queue = NULL; } + + put_disk(disk); skdev->disk = NULL; }