From: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
In commit e869b5462f83 ("blk-mq: Unregister debugfs attributes
earlier"), we shuffled the debugfs cleanup around so that the "state"
attribute was removed before we freed the blk-mq data structures.
However, later changes are going to undo that, so we need to explicitly
disallow running a dead queue.
[Omar: rebased and updated commit message]
Signed-off-by: Omar Sandoval <osandov@xxxxxx>
Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
---
block/blk-mq-debugfs.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 00cc89c34590..48b9f59acd91 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -102,6 +102,14 @@ static ssize_t queue_state_write(void *data, const char __user *buf,
struct request_queue *q = data;
char op[16] = { }, *s;
+ /*
+ * The "state" attribute is removed after blk_cleanup_queue() has called
+ * blk_mq_free_queue(). Return if QUEUE_FLAG_DEAD has been set to avoid
+ * triggering a use-after-free.
+ */
+ if (blk_queue_dead(q))
+ return -ENOENT;
+
if (copy_from_user(op, buf, min(count, sizeof(op) - 1)))
return -EFAULT;
s = op;
--
2.12.2
