Some request_fn implementations, e.g. scsi_request_fn(), unlock
the queue lock. Make sure that blk_cleanup_queue() waits until all
active request_fn invocations have finished. This fixes a potential
use-after-free at the end of scsi_request_fn(). Also, make sure that
the block layer doesn't invoke request_fn after blk_cleanup_queue()
finished.
Reported-by: Chanho Min <chanho.min@xxxxxxx>
Cc: James Bottomley <JBottomley@xxxxxxxxxxxxx>
Cc: Mike Christie <michaelc@xxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
block/blk-core.c | 32 +++++++++++++++++++++++++++++---
block/blk-exec.c | 2 +-
block/blk.h | 2 ++
drivers/scsi/scsi_lib.c | 10 +---------
include/linux/blkdev.h | 7 +++++++
5 files changed, 40 insertions(+), 13 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index b37ac03..e41b291 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -293,6 +293,27 @@ void blk_sync_queue(struct request_queue *q)
EXPORT_SYMBOL(blk_sync_queue);
/**
+ * __blk_run_queue_uncond - run a queue whether or not it has been stopped
+ * @q: The queue to run
+ *
+ * Description:
+ * Invoke request handling on a queue if there are any pending requests.
+ * May be used to restart request handling after a request has completed.
+ * This variant runs the queue whether or not the queue has been
+ * stopped. Must be called with the queue lock held and interrupts
+ * disabled. See also @blk_run_queue.
+ */
+void __blk_run_queue_uncond(struct request_queue *q)
+{
+ if (unlikely(blk_queue_dead(q)))
+ return;
+
+ q->request_fn_active++;
+ q->request_fn(q);
+ q->request_fn_active--;
+}
+
+/**
* __blk_run_queue - run a single device queue
* @q: The queue to run
*
@@ -305,7 +326,7 @@ void __blk_run_queue(struct request_queue *q)
if (unlikely(blk_queue_stopped(q)))
return;
- q->request_fn(q);
+ __blk_run_queue_uncond(q);
}
EXPORT_SYMBOL(__blk_run_queue);
@@ -388,6 +409,7 @@ void blk_drain_queue(struct request_queue *q, bool drain_all)
__blk_run_queue(q);
drain |= q->nr_rqs_elvpriv;
+ drain |= q->request_fn_active;
/*
* Unfortunately, requests are queued at and tracked from
@@ -475,8 +497,8 @@ EXPORT_SYMBOL_GPL(blk_queue_bypass_end);
* blk_cleanup_queue - shutdown a request queue
* @q: request queue to shutdown
*
- * Mark @q DEAD, drain all pending requests, destroy and put it. All
- * future requests will be failed immediately with -ENODEV.
+ * Mark @q as dying, drain all pending requests, mark @q as dead, destroy and
+ * put it. All future requests will be failed immediately with -ENODEV.
*/
void blk_cleanup_queue(struct request_queue *q)
{
@@ -508,6 +530,10 @@ void blk_cleanup_queue(struct request_queue *q)
/* drain all requests queued before DEAD marking */
blk_drain_queue(q, true);
+ spin_lock_irq(lock);
+ queue_flag_set(QUEUE_FLAG_DEAD, q);
+ spin_unlock_irq(lock);
+
/* @q won't process any more request, flush async actions */
del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);
blk_sync_queue(q);
diff --git a/block/blk-exec.c b/block/blk-exec.c
index 4aec98d..1320e74 100644
--- a/block/blk-exec.c
+++ b/block/blk-exec.c
@@ -72,7 +72,7 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
__blk_run_queue(q);
/* the queue is stopped so it won't be run */
if (rq->cmd_type == REQ_TYPE_PM_RESUME)
- q->request_fn(q);
+ __blk_run_queue_uncond(q);
spin_unlock_irq(q->queue_lock);
}
EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);
diff --git a/block/blk.h b/block/blk.h
index a066ceb..3e94c14 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -145,6 +145,8 @@ int blk_try_merge(struct request *rq, struct bio *bio);
void blk_queue_congestion_threshold(struct request_queue *q);
+void __blk_run_queue_uncond(struct request_queue *q);
+
int blk_dev_init(void);
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 593fc71..03571a3 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1517,10 +1517,6 @@ static void scsi_request_fn(struct request_queue *q)
struct scsi_cmnd *cmd;
struct request *req;
- if(!get_device(&sdev->sdev_gendev))
- /* We must be tearing the block queue down already */
- return;
-
/*
* To start with, we keep looping until the queue is empty, or until
* the host is no longer able to accept any more requests.
@@ -1629,11 +1625,7 @@ out_delay:
if (sdev->device_busy == 0)
blk_delay_queue(q, SCSI_QUEUE_DELAY);
out:
- /* must be careful here...if we trigger the ->remove() function
- * we cannot be holding the q lock */
- spin_unlock_irq(q->queue_lock);
- put_device(&sdev->sdev_gendev);
- spin_lock_irq(q->queue_lock);
+ ;
}
u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c6ab0db..ef5b80a 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -377,6 +377,11 @@ struct request_queue {
unsigned int nr_sorted;
unsigned int in_flight[2];
+ /*
+ * Number of active request_fn() calls for those request_fn()
+ * implementations that unlock the queue_lock, e.g. scsi_request_fn().
+ */
+ unsigned int request_fn_active;
unsigned int rq_timeout;
struct timer_list timeout;
@@ -451,6 +456,7 @@ struct request_queue {
#define QUEUE_FLAG_ADD_RANDOM 16 /* Contributes to random pool */
#define QUEUE_FLAG_SECDISCARD 17 /* supports SECDISCARD */
#define QUEUE_FLAG_SAME_FORCE 18 /* force complete on same CPU */
+#define QUEUE_FLAG_DEAD 19 /* queue tear-down finished */
#define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_STACKABLE) | \
@@ -521,6 +527,7 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
#define blk_queue_tagged(q) test_bit(QUEUE_FLAG_QUEUED, &(q)->queue_flags)
#define blk_queue_stopped(q) test_bit(QUEUE_FLAG_STOPPED, &(q)->queue_flags)
#define blk_queue_dying(q) test_bit(QUEUE_FLAG_DYING, &(q)->queue_flags)
+#define blk_queue_dead(q) test_bit(QUEUE_FLAG_DEAD, &(q)->queue_flags)
#define blk_queue_bypass(q) test_bit(QUEUE_FLAG_BYPASS, &(q)->queue_flags)
#define blk_queue_nomerges(q) test_bit(QUEUE_FLAG_NOMERGES, &(q)->queue_flags)
#define blk_queue_noxmerges(q) \
--
1.7.10.4
--
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
