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>
This commit is contained in:
Bart Van Assche 2018-02-28 10:15:32 -08:00 committed by Jens Axboe
parent 5ee0524ba1
commit 498f6650ae
3 changed files with 20 additions and 14 deletions

View File

@ -888,6 +888,19 @@ static void blk_rq_timed_out_timer(struct timer_list *t)
kblockd_schedule_work(&q->timeout_work);
}
/**
* blk_alloc_queue_node - allocate a request queue
* @gfp_mask: memory allocation flags
* @node_id: NUMA node to allocate memory from
* @lock: For legacy queues, pointer to a spinlock that will be used to e.g.
* serialize calls to the legacy .request_fn() callback. Ignored for
* blk-mq request queues.
*
* Note: pass the queue lock as the third argument to this function instead of
* setting the queue lock pointer explicitly to avoid triggering a sporadic
* crash in the blkcg code. This function namely calls blkcg_init_queue() and
* the queue lock pointer must be set before blkcg_init_queue() is called.
*/
struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id,
spinlock_t *lock)
{
@ -940,11 +953,8 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id,
mutex_init(&q->sysfs_lock);
spin_lock_init(&q->__queue_lock);
/*
* By default initialize queue_lock to internal lock and driver can
* override it later if need be.
*/
q->queue_lock = &q->__queue_lock;
if (!q->mq_ops)
q->queue_lock = lock ? : &q->__queue_lock;
/*
* A queue starts its life with bypass turned on to avoid
@ -1031,13 +1041,11 @@ blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
{
struct request_queue *q;
q = blk_alloc_queue_node(GFP_KERNEL, node_id, NULL);
q = blk_alloc_queue_node(GFP_KERNEL, node_id, lock);
if (!q)
return NULL;
q->request_fn = rfn;
if (lock)
q->queue_lock = lock;
if (blk_init_allocated_queue(q) < 0) {
blk_cleanup_queue(q);
return NULL;

View File

@ -2816,7 +2816,7 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
drbd_init_set_defaults(device);
q = blk_alloc_queue(GFP_KERNEL);
q = blk_alloc_queue_node(GFP_KERNEL, NUMA_NO_NODE, &resource->req_lock);
if (!q)
goto out_no_q;
device->rq_queue = q;
@ -2848,7 +2848,6 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
/* Setting the max_hw_sectors to an odd value of 8kibyte here
This triggers a max_bio_size message upon first attach or connect */
blk_queue_max_hw_sectors(q, DRBD_MAX_BIO_SIZE_SAFE >> 8);
q->queue_lock = &resource->req_lock;
device->md_io.page = alloc_page(GFP_KERNEL);
if (!device->md_io.page)

View File

@ -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 */