From 885e7b0e181c14e4d0ddd26c688bad2b84c1ada9 Mon Sep 17 00:00:00 2001
From: Roland Dreier <roland@purestorage.com>
Date: Tue, 14 Oct 2014 14:16:24 -0700
Subject: target: Don't call TFO->write_pending if data_length == 0

From: Roland Dreier <roland@purestorage.com>

commit 885e7b0e181c14e4d0ddd26c688bad2b84c1ada9 upstream.

If an initiator sends a zero-length command (e.g. TEST UNIT READY) but
sets the transfer direction in the transport layer to indicate a
data-out phase, we still shouldn't try to transfer data.  At best it's
a NOP, and depending on the transport, we might crash on an
uninitialized sg list.

Reported-by: Craig Watson <craig.watson@vanguard-rugged.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/target/target_core_transport.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -2230,7 +2230,7 @@ transport_generic_new_cmd(struct se_cmd
 	 * and let it call back once the write buffers are ready.
 	 */
 	target_add_to_state_list(cmd);
-	if (cmd->data_direction != DMA_TO_DEVICE) {
+	if (cmd->data_direction != DMA_TO_DEVICE || cmd->data_length == 0) {
 		target_execute_cmd(cmd);
 		return 0;
 	}