target: Don't call TFO->write_pending if data_length == 0

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>
Cc: <stable@vger.kernel.org> # 3.1
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 9ea0d5f..be877bf 100644 (file)
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -2292,7 +2292,7 @@ transport_generic_new_cmd(struct se_cmd *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;
        }