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:
- Rename blk_alloc_queue_node() into blk_alloc_queue_node2() and add
a new queue lock argument.
- Introduce a wrapper function with the same name and behavior as the
old blk_alloc_queue_node() function.
- Move the .queue_lock initialization from blk_init_queue_node() into
blk_alloc_queue_node2().
- For all all block drivers that initialize .queue_lock explicitly,
change the blk_alloc_queue() call in the driver into a
blk_alloc_queue_node2() 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 <[email protected]>
Signed-off-by: Bart Van Assche <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Joseph Qi <[email protected]>
Cc: Philipp Reisner <[email protected]>
Cc: Ulf Hansson <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: <[email protected]>
---
block/blk-core.c | 33 ++++++++++++++++++++++++---------
drivers/block/drbd/drbd_main.c | 4 ++--
drivers/block/umem.c | 7 +++----
drivers/mmc/core/queue.c | 3 +--
include/linux/blkdev.h | 2 ++
5 files changed, 32 insertions(+), 17 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index bd43bc50740a..cb18f57e5b13 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -946,7 +946,22 @@ static void blk_rq_timed_out_timer(struct timer_list *t)
kblockd_schedule_work(&q->timeout_work);
}
-struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
+/**
+ * blk_alloc_queue_node2 - allocate a request queue
+ * @gfp_mask: memory allocation flags
+ * @node_id: NUMA node to allocate memory from
+ * @lock: Pointer to a spinlock that will be used to e.g. serialize calls to
+ * the legacy .request_fn(). Only set this pointer for queues that use
+ * legacy mode and not for queues that use blk-mq.
+ *
+ * Note: use this function instead of calling blk_alloc_queue_node() and
+ * setting the queue lock pointer explicitly to avoid triggering a crash in
+ * the blkcg throttling code. That code namely makes sysfs attributes visible
+ * in user space before this function returns and the show method of these
+ * attributes uses the queue lock.
+ */
+struct request_queue *blk_alloc_queue_node2(gfp_t gfp_mask, int node_id,
+ spinlock_t *lock)
{
struct request_queue *q;
@@ -997,11 +1012,7 @@ 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;
+ q->queue_lock = lock ? : &q->__queue_lock;
/*
* A queue starts its life with bypass turned on to avoid
@@ -1042,6 +1053,12 @@ struct request_queue *blk_alloc_queue_node(gfp_t
gfp_mask, int node_id)
kmem_cache_free(blk_requestq_cachep, q);
return NULL;
}
+EXPORT_SYMBOL(blk_alloc_queue_node2);
+
+struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
+{
+ return blk_alloc_queue_node2(gfp_mask, node_id, NULL);
+}
EXPORT_SYMBOL(blk_alloc_queue_node);
/**
@@ -1088,13 +1105,11 @@ 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);
+ q = blk_alloc_queue_node2(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;
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 4b4697a1f963..965e80b13443 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2822,7 +2822,8 @@ 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_node2(GFP_KERNEL, NUMA_NO_NODE,
+ &resource->req_lock);
if (!q)
goto out_no_q;
device->rq_queue = q;
@@ -2854,7 +2855,6 @@ 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)
diff --git a/drivers/block/umem.c b/drivers/block/umem.c
index 8077123678ad..f6bb78782afa 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_node2(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 */
diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
index 5ecd54088988..274a8c6c8d64 100644
--- a/drivers/mmc/core/queue.c
+++ b/drivers/mmc/core/queue.c
@@ -216,10 +216,9 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card
*card,
int ret = -ENOMEM;
mq->card = card;
- mq->queue = blk_alloc_queue(GFP_KERNEL);
+ mq->queue = blk_alloc_queue_node2(GFP_KERNEL, NUMA_NO_NODE, lock);
if (!mq->queue)
return -ENOMEM;
- mq->queue->queue_lock = lock;
mq->queue->request_fn = mmc_request_fn;
mq->queue->init_rq_fn = mmc_init_request;
mq->queue->exit_rq_fn = mmc_exit_request;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 781992c4124e..37723a8b799c 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1331,6 +1331,8 @@ extern long nr_blockdev_pages(void);
bool __must_check blk_get_queue(struct request_queue *);
struct request_queue *blk_alloc_queue(gfp_t);
struct request_queue *blk_alloc_queue_node(gfp_t, int);
+struct request_queue *blk_alloc_queue_node2(gfp_t gfp_mask, int node_id,
+ spinlock_t *lock);
extern void blk_put_queue(struct request_queue *);
extern void blk_set_queue_dying(struct request_queue *);
--
2.16.0
