[PATCH 4.19 07/58] nvmet: fix a use-after-free

[Greg Kroah-Hartman]

From: Bart Van Assche <bvanassche@xxxxxxx>

[ Upstream commit 6a02a61e81c231cc5c680c5dbf8665275147ac52 ]

Fix the following use-after-free complaint triggered by blktests nvme/004:

BUG: KASAN: user-memory-access in blk_mq_complete_request_remote+0xac/0x350
Read of size 4 at addr 0000607bd1835943 by task kworker/13:1/460
Workqueue: nvmet-wq nvme_loop_execute_work [nvme_loop]
Call Trace:
 show_stack+0x52/0x58
 dump_stack_lvl+0x49/0x5e
 print_report.cold+0x36/0x1e2
 kasan_report+0xb9/0xf0
 __asan_load4+0x6b/0x80
 blk_mq_complete_request_remote+0xac/0x350
 nvme_loop_queue_response+0x1df/0x275 [nvme_loop]
 __nvmet_req_complete+0x132/0x4f0 [nvmet]
 nvmet_req_complete+0x15/0x40 [nvmet]
 nvmet_execute_io_connect+0x18a/0x1f0 [nvmet]
 nvme_loop_execute_work+0x20/0x30 [nvme_loop]
 process_one_work+0x56e/0xa70
 worker_thread+0x2d1/0x640
 kthread+0x183/0x1c0
 ret_from_fork+0x1f/0x30

Cc: stable@xxxxxxxxxxxxxxx
Fixes: a07b4970f464 ("nvmet: add a generic NVMe target")
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/nvme/target/core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index 1a35d73c39c3..80b5aae1bdc9 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -504,6 +504,7 @@ static void __nvmet_req_complete(struct nvmet_req *req, u16 status)
 {
 	u32 old_sqhd, new_sqhd;
 	u16 sqhd;
+	struct nvmet_ns *ns = req->ns;
 
 	if (status)
 		nvmet_set_status(req, status);
@@ -520,9 +521,9 @@ static void __nvmet_req_complete(struct nvmet_req *req, u16 status)
 	req->rsp->sq_id = cpu_to_le16(req->sq->qid);
 	req->rsp->command_id = req->cmd->common.command_id;
 
-	if (req->ns)
-		nvmet_put_namespace(req->ns);
 	req->ops->queue_response(req);
+	if (ns)
+		nvmet_put_namespace(ns);
 }
 
 void nvmet_req_complete(struct nvmet_req *req, u16 status)
-- 
2.35.1