iscsi-target: Fix potential NULL pointer in solicited NOPOUT reject

This patch addresses a potential NULL pointer dereference regression in
iscsit_setup_nop_out() code, specifically for two cases when a solicited
NOPOUT triggers a ISCSI_REASON_PROTOCOL_ERROR reject to be generated.

This is because iscsi_cmd is expected to be NULL for solicited NOPOUT
case before iscsit_process_nop_out() locates the descriptor via TTT
using iscsit_find_cmd_from_ttt().

This regression was originally introduced in:

commit ba159914086f06532079fc15141f46ffe7e04a41
Author: Nicholas Bellinger <nab@linux-iscsi.org>
Date:   Wed Jul 3 03:48:24 2013 -0700

    iscsi-target: Fix iscsit_add_reject* usage for iser

Cc: stable@vger.kernel.org  # 3.10+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 8fd359cb7da0..3a179302b904 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -1522,6 +1522,10 @@ int iscsit_setup_nop_out(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
         if (hdr->itt == RESERVED_ITT && !(hdr->opcode & ISCSI_OP_IMMEDIATE)) {
                 pr_err("NOPOUT ITT is reserved, but Immediate Bit is"
                         " not set, protocol error.\n");
+                if (!cmd)
+                        return iscsit_add_reject(conn, ISCSI_REASON_PROTOCOL_ERROR,
+                                                 (unsigned char *)hdr);
+
                 return iscsit_reject_cmd(cmd, ISCSI_REASON_PROTOCOL_ERROR,
                                          (unsigned char *)hdr);
         }
@@ -1531,6 +1535,10 @@ int iscsit_setup_nop_out(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
                         " greater than MaxXmitDataSegmentLength: %u, protocol"
                         " error.\n", payload_length,
                         conn->conn_ops->MaxXmitDataSegmentLength);
+                if (!cmd)
+                        return iscsit_add_reject(conn, ISCSI_REASON_PROTOCOL_ERROR,
+                                                 (unsigned char *)hdr);
+
                 return iscsit_reject_cmd(cmd, ISCSI_REASON_PROTOCOL_ERROR,
                                          (unsigned char *)hdr);
         }