block: Fix a race between the cgroup code and request queue initialization

Initialize the request queue lock earlier such that the following
race can no longer occur:

blk_init_queue_node()             blkcg_print_blkgs()
  blk_alloc_queue_node (1)
    q->queue_lock = &q->__queue_lock (2)
    blkcg_init_queue(q) (3)
                                    spin_lock_irq(blkg->q->queue_lock) (4)
  q->queue_lock = lock (5)
                                    spin_unlock_irq(blkg->q->queue_lock) (6)

(1) allocate an uninitialized queue;
(2) initialize queue_lock to its default internal lock;
(3) initialize blkcg part of request queue, which will create blkg and
    then insert it to blkg_list;
(4) traverse blkg_list and find the created blkg, and then take its
    queue lock, here it is the default *internal lock*;
(5) *race window*, now queue_lock is overridden with *driver specified
    lock*;
(6) now unlock *driver specified lock*, not the locked *internal lock*,
    unlock balance breaks.

The changes in this patch are as follows:
- Move the .queue_lock initialization from blk_init_queue_node() into
  blk_alloc_queue_node().
- Only override the .queue_lock pointer for legacy queues because it
  is not useful for blk-mq queues to override this pointer.
- For all all block drivers that initialize .queue_lock explicitly,
  change the blk_alloc_queue() call in the driver into a
  blk_alloc_queue_node() call and remove the explicit .queue_lock
  initialization. Additionally, initialize the spin lock that will
  be used as queue lock earlier if necessary.

Reported-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 3 insertions, 4 deletions

diff --git a/drivers/block/umem.c b/drivers/block/umem.c
index 8077123678ad..5c7fb8cc4149 100644
--- a/drivers/block/umem.c
+++ b/drivers/block/umem.c
@@ -888,13 +888,14 @@ static int mm_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
 	card->Active = -1;	/* no page is active */
 	card->bio = NULL;
 	card->biotail = &card->bio;
+	spin_lock_init(&card->lock);
 
-	card->queue = blk_alloc_queue(GFP_KERNEL);
+	card->queue = blk_alloc_queue_node(GFP_KERNEL, NUMA_NO_NODE,
+					   &card->lock);
 	if (!card->queue)
 		goto failed_alloc;
 
 	blk_queue_make_request(card->queue, mm_make_request);
-	card->queue->queue_lock = &card->lock;
 	card->queue->queuedata = card;
 
 	tasklet_init(&card->tasklet, process_page, (unsigned long)card);
@@ -968,8 +969,6 @@ static int mm_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
 	dev_printk(KERN_INFO, &card->dev->dev,
 		"Window size %d bytes, IRQ %d\n", data, dev->irq);
 
-	spin_lock_init(&card->lock);
-
 	pci_set_drvdata(dev, card);
 
 	if (pci_write_cmd != 0x0F) 	/* If not Memory Write & Invalidate */