iscsi-target: Do not reject non-immediate CmdSNs exceeding MaxCmdSN

This patch changes iscsit_sequence_cmd() logic to no longer reject
non-immediate CmdSNs that exceed MaxCmdSN with a protocol error,
but instead silently ignore them.

This is done to correctly follow RFC-3720 Section 3.2.2.1:

   For non-immediate commands, the CmdSN field can take any
   value from ExpCmdSN to MaxCmdSN inclusive.  The target MUST silently
   ignore any non-immediate command outside of this range or non-
   immediate duplicates within the range.

Reported-by: Santosh Kulkarni <santosh.kulkarni@calsoftinc.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

2 files changed, 11 insertions, 8 deletions

diff --git a/drivers/target/iscsi/iscsi_target_core.h b/drivers/target/iscsi/iscsi_target_core.h
index f2094d2f8eef..8dcb3c1aa801 100644
--- a/drivers/target/iscsi/iscsi_target_core.h
+++ b/drivers/target/iscsi/iscsi_target_core.h
@@ -193,6 +193,7 @@ enum recover_cmdsn_ret_table {
         CMDSN_NORMAL_OPERATION          = 0,
         CMDSN_LOWER_THAN_EXP            = 1,
         CMDSN_HIGHER_THAN_EXP           = 2,
+        CMDSN_MAXCMDSN_OVERRUN          = 3,
 };
 
 /* Used for iscsi_handle_immediate_data() return values */
diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c
index 45b8fd13fa72..9064926a0370 100644
--- a/drivers/target/iscsi/iscsi_target_util.c
+++ b/drivers/target/iscsi/iscsi_target_util.c
@@ -242,9 +242,9 @@ static inline int iscsit_check_received_cmdsn(struct iscsi_session *sess, u32 cm
          */
         if (iscsi_sna_gt(cmdsn, sess->max_cmd_sn)) {
                 pr_err("Received CmdSN: 0x%08x is greater than"
-                       " MaxCmdSN: 0x%08x, protocol error.\n", cmdsn,
+                       " MaxCmdSN: 0x%08x, ignoring.\n", cmdsn,
                        sess->max_cmd_sn);
-                ret = CMDSN_ERROR_CANNOT_RECOVER;
+                ret = CMDSN_MAXCMDSN_OVERRUN;
 
         } else if (cmdsn == sess->exp_cmd_sn) {
                 sess->exp_cmd_sn++;
@@ -303,14 +303,16 @@ int iscsit_sequence_cmd(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
                 ret = CMDSN_HIGHER_THAN_EXP;
                 break;
         case CMDSN_LOWER_THAN_EXP:
+        case CMDSN_MAXCMDSN_OVERRUN:
+        default:
                 cmd->i_state = ISTATE_REMOVE;
                 iscsit_add_cmd_to_immediate_queue(cmd, conn, cmd->i_state);
-                ret = cmdsn_ret;
-                break;
-        default:
-                reason = ISCSI_REASON_PROTOCOL_ERROR;
-                reject = true;
-                ret = cmdsn_ret;
+                /*
+                 * Existing callers for iscsit_sequence_cmd() will silently
+                 * ignore commands with CMDSN_LOWER_THAN_EXP, so force this
+                 * return for CMDSN_MAXCMDSN_OVERRUN as well..
+                 */
+                ret = CMDSN_LOWER_THAN_EXP;
                 break;
         }
         mutex_unlock(&conn->sess->cmdsn_mutex);