[PATCH 4.14 040/138] blk-mq: fix race between updating nr_hw_queues and switching io sched

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

--

From: Ming Lei 


[ Upstream commit fb350e0ad99359768e1e80b4784692031ec340e4 ]

In both elevator_switch_mq() and blk_mq_update_nr_hw_queues(), sched tags
can be allocated, and q->nr_hw_queue is used, and race is inevitable, for
example: blk_mq_init_sched() may trigger use-after-free on hctx, which is
freed in blk_mq_realloc_hw_ctxs() when nr_hw_queues is decreased.

This patch fixes the race be holding q->sysfs_lock.

Reviewed-by: Christoph Hellwig 
Reported-by: Yi Zhang 
Tested-by: Yi Zhang 
Signed-off-by: Ming Lei 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman 
---
 block/blk-mq.c |4 
 1 file changed, 4 insertions(+)

--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2314,6 +2314,9 @@ static void blk_mq_realloc_hw_ctxs(struc
struct blk_mq_hw_ctx **hctxs = q->queue_hw_ctx;
 
blk_mq_sysfs_unregister(q);
+
+   /* protect against switching io scheduler  */
+   mutex_lock(>sysfs_lock);
for (i = 0; i < set->nr_hw_queues; i++) {
int node;
 
@@ -2358,6 +2361,7 @@ static void blk_mq_realloc_hw_ctxs(struc
}
}
q->nr_hw_queues = i;
+   mutex_unlock(>sysfs_lock);
blk_mq_sysfs_register(q);
 }
 

[PATCH 4.14 040/138] blk-mq: fix race between updating nr_hw_queues and switching io sched

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

--

From: Ming Lei 


[ Upstream commit fb350e0ad99359768e1e80b4784692031ec340e4 ]

In both elevator_switch_mq() and blk_mq_update_nr_hw_queues(), sched tags
can be allocated, and q->nr_hw_queue is used, and race is inevitable, for
example: blk_mq_init_sched() may trigger use-after-free on hctx, which is
freed in blk_mq_realloc_hw_ctxs() when nr_hw_queues is decreased.

This patch fixes the race be holding q->sysfs_lock.

Reviewed-by: Christoph Hellwig 
Reported-by: Yi Zhang 
Tested-by: Yi Zhang 
Signed-off-by: Ming Lei 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman 
---
 block/blk-mq.c |4 
 1 file changed, 4 insertions(+)

--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2314,6 +2314,9 @@ static void blk_mq_realloc_hw_ctxs(struc
struct blk_mq_hw_ctx **hctxs = q->queue_hw_ctx;
 
blk_mq_sysfs_unregister(q);
+
+   /* protect against switching io scheduler  */
+   mutex_lock(>sysfs_lock);
for (i = 0; i < set->nr_hw_queues; i++) {
int node;
 
@@ -2358,6 +2361,7 @@ static void blk_mq_realloc_hw_ctxs(struc
}
}
q->nr_hw_queues = i;
+   mutex_unlock(>sysfs_lock);
blk_mq_sysfs_register(q);
 }