nvmet-tcp: fix regression in data_digest calculation

Data digest calculation iterates over command mapped iovec. However
since commit bac04454 we unmap the iovec before we handle the data
digest, and since commit 69b85e1f we clear nr_mapped when we unmap
the iov.

Instead of open-coding the command iov traversal, simply call
crypto_ahash_digest with the command sg that is already allocated (we
already do that for the send path). Rename nvmet_tcp_send_ddgst to
nvmet_tcp_calc_ddgst and call it from send and recv paths.

Fixes: 69b85e1f ("nvmet-tcp: add an helper to free the cmd buffers")
Fixes: bac04454 ("nvmet-tcp: fix kmap leak when data digest in use")
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/target/tcp.c

@@ -405,7 +405,7 @@ static int nvmet_tcp_map_data(struct nvmet_tcp_cmd *cmd)
 	return NVME_SC_INTERNAL;
 }
 
-static void nvmet_tcp_send_ddgst(struct ahash_request *hash,
+static void nvmet_tcp_calc_ddgst(struct ahash_request *hash,
 		struct nvmet_tcp_cmd *cmd)
 {
 	ahash_request_set_crypt(hash, cmd->req.sg,
@@ -413,23 +413,6 @@ static void nvmet_tcp_send_ddgst(struct ahash_request *hash,
 	crypto_ahash_digest(hash);
 }
 
-static void nvmet_tcp_recv_ddgst(struct ahash_request *hash,
-		struct nvmet_tcp_cmd *cmd)
-{
-	struct scatterlist sg;
-	struct kvec *iov;
-	int i;
-
-	crypto_ahash_init(hash);
-	for (i = 0, iov = cmd->iov; i < cmd->nr_mapped; i++, iov++) {
-		sg_init_one(&sg, iov->iov_base, iov->iov_len);
-		ahash_request_set_crypt(hash, &sg, NULL, iov->iov_len);
-		crypto_ahash_update(hash);
-	}
-	ahash_request_set_crypt(hash, NULL, (void *)&cmd->exp_ddgst, 0);
-	crypto_ahash_final(hash);
-}
-
 static void nvmet_setup_c2h_data_pdu(struct nvmet_tcp_cmd *cmd)
 {
 	struct nvme_tcp_data_pdu *pdu = cmd->data_pdu;
@@ -454,7 +437,7 @@ static void nvmet_setup_c2h_data_pdu(struct nvmet_tcp_cmd *cmd)
 
 	if (queue->data_digest) {
 		pdu->hdr.flags |= NVME_TCP_F_DDGST;
-		nvmet_tcp_send_ddgst(queue->snd_hash, cmd);
+		nvmet_tcp_calc_ddgst(queue->snd_hash, cmd);
 	}
 
 	if (cmd->queue->hdr_digest) {
@@ -1137,7 +1120,7 @@ static void nvmet_tcp_prep_recv_ddgst(struct nvmet_tcp_cmd *cmd)
 {
 	struct nvmet_tcp_queue *queue = cmd->queue;
 
-	nvmet_tcp_recv_ddgst(queue->rcv_hash, cmd);
+	nvmet_tcp_calc_ddgst(queue->rcv_hash, cmd);
 	queue->offset = 0;
 	queue->left = NVME_TCP_DIGEST_LENGTH;
 	queue->rcv_state = NVMET_TCP_RECV_DDGST;