[PATCH 5.10.y 2/2] nvme-tcp: fix host memory disclosure on R2T for a read command

[Sasha Levin <sashal@kernel.org>]

From: Yehyeong Lee <yhlee@isslab.korea.ac.kr>

[ Upstream commit 6efbc52237facda35d2d874fe1765bb4839275d8 ]

nvme_tcp_handle_r2t() does not check the direction of the request the
R2T refers to. A malicious controller can send an R2T for a READ and
the host will answer it: nvme_tcp_setup_h2c_data_pdu() builds the
H2CData header and nvme_tcp_try_send_data() sends the request's data
buffer. That buffer is the READ destination, so its contents go to the
controller.

The command then completes normally and nothing is logged.

Against a test controller that answers every READ with an R2T, a 4096
byte buffered read returned all 4096 bytes, split over two R2Ts. The
pages contained stale kernel data, including an array of struct page
pointers.

Reject an R2T for a request that is not a write.

Fixes: 3f2304f8c6d6 ("nvme-tcp: add NVMe over TCP host driver")
Cc: stable@vger.kernel.org
Signed-off-by: Yehyeong Lee <yhlee@isslab.korea.ac.kr>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/nvme/host/tcp.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 01d42b854be2d..c9436767534a7 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -645,6 +645,13 @@ static int nvme_tcp_handle_r2t(struct nvme_tcp_queue *queue,
 	}
 	req = blk_mq_rq_to_pdu(rq);
 
+	if (unlikely(rq_data_dir(rq) != WRITE)) {
+		dev_err(queue->ctrl->ctrl.device,
+			"req %d unexpected r2t for a non-write command\n",
+			rq->tag);
+		return -EPROTO;
+	}
+
 	if (unlikely(!r2t_length)) {
 		dev_err(queue->ctrl->ctrl.device,
 			"req %d r2t len is %u, probably a bug...\n",
-- 
2.53.0