This is a note to let you know that I've just added the patch titled skd: Avoid that module unloading triggers a use-after-free to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: skd-avoid-that-module-unloading-triggers-a-use-after-free.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 7277cc67b3916eed47558c64f9c9c0de00a35cda Mon Sep 17 00:00:00 2001 From: Bart Van Assche <bart.vanassche@xxxxxxx> Date: Thu, 17 Aug 2017 13:12:45 -0700 Subject: skd: Avoid that module unloading triggers a use-after-free From: Bart Van Assche <bart.vanassche@xxxxxxx> 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@xxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: Hannes Reinecke <hare@xxxxxxx> Cc: Johannes Thumshirn <jthumshirn@xxxxxxx> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/block/skd_main.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) --- a/drivers/block/skd_main.c +++ b/drivers/block/skd_main.c @@ -4622,15 +4622,16 @@ 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; } Patches currently in stable-queue which might be from bart.vanassche@xxxxxxx are queue-4.9/scsi-sg-factor-out-sg_fill_request_table.patch queue-4.9/skd-submit-requests-to-firmware-before-triggering-the-doorbell.patch queue-4.9/block-relax-a-check-in-blk_start_queue.patch queue-4.9/skd-avoid-that-module-unloading-triggers-a-use-after-free.patch