scsi: target: Fix NULL pointer dereference

NULL pointer dereference happens when the following conditions are met:

1) A SCSI command is received for a non-existing LU or cdb initialization
   fails in target_setup_cmd_from_cdb().

2) Tracing is enabled.

The following call sequences lead to NULL pointer dereference:

1) iscsit_setup_scsi_cmd
     transport_lookup_cmd_lun <-- lookup fails.
          or
     target_setup_cmd_from_cdb() <-- cdb initialization fails
   iscsit_process_scsi_cmd
     iscsit_sequence_cmd
       transport_send_check_condition_and_sense
         trace_target_cmd_complete <-- NULL dereference

2) target_submit_cmd_map_sgls
     transport_lookup_cmd_lun <-- lookup fails
          or
     target_setup_cmd_from_cdb() <-- cdb initialization fails
       transport_send_check_condition_and_sense
         trace_target_cmd_complete <-- NULL dereference

In the above sequence, cmd->t_task_cdb is uninitialized which when
referenced in trace_target_cmd_complete() causes NULL pointer dereference.

The fix is to use the helper, target_cmd_init_cdb() and call it after
transport_init_se_cmd() is called, so that cmd->t_task_cdb can be
initialized and hence can be referenced in trace_target_cmd_complete().

Link: https://lore.kernel.org/r/1591559913-8388-4-git-send-email-sudhakar.panneerselvam@oracle.com
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Sudhakar Panneerselvam <sudhakar.panneerselvam@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 1b45362..93534dc 100644 (file)
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -1167,6 +1167,16 @@ int iscsit_setup_scsi_cmd(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
 
        target_get_sess_cmd(&cmd->se_cmd, true);
 
+       cmd->sense_reason = target_cmd_init_cdb(&cmd->se_cmd, hdr->cdb);
+       if (cmd->sense_reason) {
+               if (cmd->sense_reason == TCM_OUT_OF_RESOURCES) {
+                       return iscsit_add_reject_cmd(cmd,
+                               ISCSI_REASON_BOOKMARK_NO_RESOURCES, buf);
+               }
+
+               goto attach_cmd;
+       }
+
        cmd->sense_reason = transport_lookup_cmd_lun(&cmd->se_cmd);
        if (cmd->sense_reason)
                goto attach_cmd;
@@ -1174,14 +1184,8 @@ int iscsit_setup_scsi_cmd(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
        /* only used for printks or comparing with ->ref_task_tag */
        cmd->se_cmd.tag = (__force u32)cmd->init_task_tag;
        cmd->sense_reason = target_setup_cmd_from_cdb(&cmd->se_cmd, hdr->cdb);
-       if (cmd->sense_reason) {
-               if (cmd->sense_reason == TCM_OUT_OF_RESOURCES) {
-                       return iscsit_add_reject_cmd(cmd,
-                                       ISCSI_REASON_BOOKMARK_NO_RESOURCES, buf);
-               }
-
+       if (cmd->sense_reason)
                goto attach_cmd;
-       }
 
        if (iscsit_build_pdu_and_seq_lists(cmd, payload_length) < 0) {
                return iscsit_add_reject_cmd(cmd,

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 7ea7793..0fbb382 100644 (file)
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1413,6 +1413,9 @@ transport_check_alloc_task_attr(struct se_cmd *cmd)
 sense_reason_t
 target_cmd_init_cdb(struct se_cmd *cmd, unsigned char *cdb)
 {
+       sense_reason_t ret;
+
+       cmd->t_task_cdb = &cmd->__t_task_cdb[0];
        /*
         * Ensure that the received CDB is less than the max (252 + 8) bytes
         * for VARIABLE_LENGTH_CMD
@@ -1421,7 +1424,8 @@ target_cmd_init_cdb(struct se_cmd *cmd, unsigned char *cdb)
                pr_err("Received SCSI CDB with command_size: %d that"
                        " exceeds SCSI_MAX_VARLEN_CDB_SIZE: %d\n",
                        scsi_command_size(cdb), SCSI_MAX_VARLEN_CDB_SIZE);
-               return TCM_INVALID_CDB_FIELD;
+               ret = TCM_INVALID_CDB_FIELD;
+               goto err;
        }
        /*
         * If the received CDB is larger than TCM_MAX_COMMAND_SIZE,
@@ -1436,10 +1440,10 @@ target_cmd_init_cdb(struct se_cmd *cmd, unsigned char *cdb)
                                " %u > sizeof(cmd->__t_task_cdb): %lu ops\n",
                                scsi_command_size(cdb),
                                (unsigned long)sizeof(cmd->__t_task_cdb));
-                       return TCM_OUT_OF_RESOURCES;
+                       ret = TCM_OUT_OF_RESOURCES;
+                       goto err;
                }
-       } else
-               cmd->t_task_cdb = &cmd->__t_task_cdb[0];
+       }
        /*
         * Copy the original CDB into cmd->
         */
@@ -1447,6 +1451,15 @@ target_cmd_init_cdb(struct se_cmd *cmd, unsigned char *cdb)
 
        trace_target_sequencer_start(cmd);
        return 0;
+
+err:
+       /*
+        * Copy the CDB here to allow trace_target_cmd_complete() to
+        * print the cdb to the trace buffers.
+        */
+       memcpy(cmd->t_task_cdb, cdb, min(scsi_command_size(cdb),
+                                        (unsigned int)TCM_MAX_COMMAND_SIZE));
+       return ret;
 }
 EXPORT_SYMBOL(target_cmd_init_cdb);
 
@@ -1456,8 +1469,6 @@ target_setup_cmd_from_cdb(struct se_cmd *cmd, unsigned char *cdb)
        struct se_device *dev = cmd->se_dev;
        sense_reason_t ret;
 
-       target_cmd_init_cdb(cmd, cdb);
-
        ret = dev->transport->parse_cdb(cmd);
        if (ret == TCM_UNSUPPORTED_SCSI_OPCODE)
                pr_warn_ratelimited("%s/%s: Unsupported SCSI Opcode 0x%02x, sending CHECK_CONDITION.\n",
@@ -1621,6 +1632,14 @@ int target_submit_cmd_map_sgls(struct se_cmd *se_cmd, struct se_session *se_sess
         */
        if (flags & TARGET_SCF_BIDI_OP)
                se_cmd->se_cmd_flags |= SCF_BIDI;
+
+       rc = target_cmd_init_cdb(se_cmd, cdb);
+       if (rc) {
+               transport_send_check_condition_and_sense(se_cmd, rc, 0);
+               target_put_sess_cmd(se_cmd);
+               return 0;
+       }
+
        /*
         * Locate se_lun pointer and attach it to struct se_cmd
         */

diff --git a/drivers/target/target_core_xcopy.c b/drivers/target/target_core_xcopy.c
index 5f1bab3..7f9c93b 100644 (file)
--- a/drivers/target/target_core_xcopy.c
+++ b/drivers/target/target_core_xcopy.c
@@ -526,6 +526,9 @@ static int target_xcopy_setup_pt_cmd(
        }
        cmd->se_cmd_flags |= SCF_SE_LUN_CMD;
 
+       if (target_cmd_init_cdb(cmd, cdb))
+               return -EINVAL;
+
        cmd->tag = 0;
        if (target_setup_cmd_from_cdb(cmd, cdb))
                return -EINVAL;