[PATCH] nvme-tcp: Fix H2CData PDU send accounting (again)

[Sagi Grimberg]

We should not access request members after the last send, even to
determine if indeed it was the last data payload send. The reason is
that a completion could have arrived and trigger a new execution of the
request which overridden these members. This was fixed by commit
825619b09ad3 ("nvme-tcp: fix possible use-after-completion").

Commit e371af033c56 broke that assumption again to address cases where
multiple r2t pdus are sent per request. To fix it, we need to record the
request data_sent and data_len and after the payload network send we
reference these counters to determine weather we should advance the
request iterator.

Fixes: e371af033c56 ("nvme-tcp: fix incorrect h2cdata pdu offset accounting")
Reported-by: Keith Busch <kbusch at kernel.org>
Cc: stable at vger.kernel.org # 5.10+ 
Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
---
 drivers/nvme/host/tcp.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 78966b8ddb1e..42b58eb1ba62 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -926,15 +926,17 @@ static void nvme_tcp_fail_request(struct nvme_tcp_request *req)
 static int nvme_tcp_try_send_data(struct nvme_tcp_request *req)
 {
 	struct nvme_tcp_queue *queue = req->queue;
+	int req_data_len = req->data_len;
 
 	while (true) {
 		struct page *page = nvme_tcp_req_cur_page(req);
 		size_t offset = nvme_tcp_req_cur_offset(req);
 		size_t len = nvme_tcp_req_cur_length(req);
-		bool last = nvme_tcp_pdu_last_send(req, len);
+		bool pdu_last = nvme_tcp_pdu_last_send(req, len);
+		int req_data_sent = req->data_sent;
 		int ret, flags = MSG_DONTWAIT;
 
-		if (last && !queue->data_digest && !nvme_tcp_queue_more(queue))
+		if (pdu_last && !queue->data_digest && !nvme_tcp_queue_more(queue))
 			flags |= MSG_EOR;
 		else
 			flags |= MSG_MORE | MSG_SENDPAGE_NOTLAST;
@@ -958,11 +960,11 @@ static int nvme_tcp_try_send_data(struct nvme_tcp_request *req)
 		 * in the request where we don't want to modify it as we may
 		 * compete with the RX path completing the request.
 		 */
-		if (req->data_sent + ret < req->data_len)
+		if (req_data_sent + ret < req_data_len)
 			nvme_tcp_advance_req(req, ret);
 
 		/* fully successful last send in current PDU */
-		if (last && ret == len) {
+		if (pdu_last && ret == len) {
 			if (queue->data_digest) {
 				nvme_tcp_ddgst_final(queue->snd_hash,
 					&req->ddgst);
-- 
2.30.2