[PATCH] nvmet-fc: Fix potential Use-after-free bug in nvmet_fc_delete_target_queue()

[Liang He <windhl@126.com>]

In nvmet_fc_delete_target_queue(), the nvmet_fc_tgt_q_put() may free
queue if its refcount hits 0. And the following code will dereference
it to get qclock by 'queue->qlock', so there is a potential UAF bug.

Fixes: 619c62dcc62b ("nvmet-fc: correct ref counting error when deferred rcv used")
Signed-off-by: Liang He <windhl@126.com>
---
 drivers/nvme/target/fc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/fc.c b/drivers/nvme/target/fc.c
index ab2627e17bb9..32e1d62017d2 100644
--- a/drivers/nvme/target/fc.c
+++ b/drivers/nvme/target/fc.c
@@ -881,6 +881,7 @@ nvmet_fc_delete_target_queue(struct nvmet_fc_tgt_queue *queue)
 	struct nvmet_fc_tgtport *tgtport = queue->assoc->tgtport;
 	struct nvmet_fc_fcp_iod *fod = queue->fod;
 	struct nvmet_fc_defer_fcp_req *deferfcp, *tempptr;
+	spinlock_t *q_lock = &queue->qlock;
 	unsigned long flags;
 	int i;
 	bool disconnect;
@@ -942,7 +943,7 @@ nvmet_fc_delete_target_queue(struct nvmet_fc_tgt_queue *queue)
 
 		kfree(deferfcp);
 
-		spin_lock_irqsave(&queue->qlock, flags);
+		spin_lock_irqsave(q_lock, flags);
 	}
 	spin_unlock_irqrestore(&queue->qlock, flags);
 
-- 
2.25.1