target/iscsi: Fix double free of a TUR followed by a solicited NOPOUT

commit 9547308b upstream.

Make sure all non-READ SCSI commands get targ_xfer_tag initialized
to 0xffffffff, not just WRITEs.

Double-free of a TUR cmd object occurs under the following scenario:

1. TUR received (targ_xfer_tag is uninitialized and left at 0)
2. TUR status sent
3. First unsolicited NOPIN is sent to initiator (gets targ_xfer_tag of 0)
4. NOPOUT for NOPIN (with TTT=0) arrives
 - its ExpStatSN acks TUR status, TUR is queued for removal
 - LIO tries to find NOPIN with TTT=0, but finds the same TUR instead,
   TUR is queued for removal for the 2nd time

(Drop unbalanced conditional bracket usage - nab)
Signed-off-by: Alexei Potashnik <alexei@purestorage.com>
Signed-off-by: Spencer Baugh <sbaugh@catern.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
[bwh: Backported to 3.2:
 - Adjust context
 - Keep the braces around the if-block]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/target/iscsi/iscsi_target.c

@@ -979,7 +979,7 @@ static int iscsit_handle_scsi_cmd(
 		if (cmd->targ_xfer_tag == 0xFFFFFFFF)
 			cmd->targ_xfer_tag = conn->sess->targ_xfer_tag++;
 		spin_unlock_bh(&conn->sess->ttt_lock);
-	} else if (hdr->flags & ISCSI_FLAG_CMD_WRITE)
+	} else
 		cmd->targ_xfer_tag = 0xFFFFFFFF;
 	cmd->cmd_sn		= hdr->cmdsn;
 	cmd->exp_stat_sn	= hdr->exp_statsn;