[PATCH] nvmet: Avoid potential UAF in nvmet_req_complete()

[Damien Le Moal]

A host ->queue_response() operation implementation may free the request
passed as argument. Such implementation potentially could result
in use after free of the request pointer when percpu_ref_put() is called
in nvmet_req_complete().

Avoid such problem by using a local variable to save the sq pointer
before calling __nvmet_req_complete(), thus avoiding dereferencing the
req pointer.

Signed-off-by: Damien Le Moal <damien.lemoal at opensource.wdc.com>
---
 drivers/nvme/target/core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index 597d1b2c0d52..0f9193323a02 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -758,8 +758,10 @@ static void __nvmet_req_complete(struct nvmet_req *req, u16 status)
 
 void nvmet_req_complete(struct nvmet_req *req, u16 status)
 {
+	struct nvmet_sq *sq = req->sq;
+
 	__nvmet_req_complete(req, status);
-	percpu_ref_put(&req->sq->ref);
+	percpu_ref_put(&sq->ref);
 }
 EXPORT_SYMBOL_GPL(nvmet_req_complete);
 
-- 
2.39.2