app-layer: fix coverity warnings

src/app-layer-dcerpc-udp.c

@@ -716,6 +716,8 @@ static int DCERPCUDPParse(Flow *f, void *dcerpc_state,
 
     if (input == NULL && AppLayerParserStateIssetFlag(pstate, APP_LAYER_PARSER_EOF)) {
         SCReturnInt(1);
+    } else if (input == NULL || input_len == 0) {
+        SCReturnInt(-1);
     }
 
 	DCERPCUDPState *sstate = (DCERPCUDPState *) dcerpc_state;

src/app-layer-dcerpc.c

@@ -1913,6 +1913,8 @@ static int DCERPCParse(Flow *f, void *dcerpc_state,
 
     if (input == NULL && AppLayerParserStateIssetFlag(pstate, APP_LAYER_PARSER_EOF)) {
         SCReturnInt(1);
+    } else if (input == NULL || input_len == 0) {
+        SCReturnInt(-1);
     }
 
     if (sstate->dcerpc.bytesprocessed != 0 && sstate->data_needed_for_dir != dir) {

src/app-layer-dns-tcp.c

@@ -503,7 +503,7 @@ static int DNSTCPResponseParse(Flow *f, void *dstate,
         SCReturnInt(-1);
 
     /* probably a rst/fin sending an eof */
-    if (input_len == 0) {
+    if (input == NULL || input_len == 0) {
         goto insufficient_data;
     }
 

src/app-layer-ftp.c

@@ -221,6 +221,8 @@ static int FTPParseRequest(Flow *f, void *ftp_state,
 
     if (input == NULL && AppLayerParserStateIssetFlag(pstate, APP_LAYER_PARSER_EOF)) {
         SCReturnInt(1);
+    } else if (input == NULL || input_len == 0) {
+        SCReturnInt(-1);
     }
 
     state->input = input;

src/app-layer-modbus.c

@@ -1229,6 +1229,8 @@ static int ModbusParseRequest(Flow                  *f,
 
     if (input == NULL && AppLayerParserStateIssetFlag(pstate, APP_LAYER_PARSER_EOF)) {
         SCReturnInt(1);
+    } else if (input == NULL || input_len == 0) {
+        SCReturnInt(-1);
     }
 
     while (input_len > 0) {
@@ -1290,6 +1292,8 @@ static int ModbusParseResponse(Flow                 *f,
 
     if (input == NULL && AppLayerParserStateIssetFlag(pstate, APP_LAYER_PARSER_EOF)) {
         SCReturnInt(1);
+    } else if (input == NULL || input_len == 0) {
+        SCReturnInt(-1);
     }
 
     while (input_len > 0) {

src/app-layer-smb2.c

@@ -534,6 +534,8 @@ static int SMB2Parse(Flow *f, void *smb2_state, AppLayerParserState *pstate,
 
     if (input == NULL && AppLayerParserStateIssetFlag(pstate, APP_LAYER_PARSER_EOF)) {
         SCReturnInt(1);
+    } else if (input == NULL || input_len == 0) {
+        SCReturnInt(-1);
     }
 
     while (sstate->bytesprocessed <  NBSS_HDR_LEN && input_len) {

src/app-layer-smtp.c

@@ -1067,6 +1067,8 @@ static int SMTPParse(int direction, Flow *f, SMTPState *state,
 
     if (input == NULL && AppLayerParserStateIssetFlag(pstate, APP_LAYER_PARSER_EOF)) {
         SCReturnInt(1);
+    } else if (input == NULL || input_len == 0) {
+        SCReturnInt(-1);
     }
 
     state->input = input;

src/app-layer-ssh.c

@@ -424,6 +424,8 @@ static int SSHParseRequest(Flow *f, void *state, AppLayerParserState *pstate,
 
     if (input == NULL && AppLayerParserStateIssetFlag(pstate, APP_LAYER_PARSER_EOF)) {
         SCReturnInt(1);
+    } else if (input == NULL || input_len == 0) {
+        SCReturnInt(-1);
     }
 
     int r = SSHParseData(ssh_state, ssh_header, input, input_len);
@@ -446,6 +448,8 @@ static int SSHParseResponse(Flow *f, void *state, AppLayerParserState *pstate,
 
     if (input == NULL && AppLayerParserStateIssetFlag(pstate, APP_LAYER_PARSER_EOF)) {
         SCReturnInt(1);
+    } else if (input == NULL || input_len == 0) {
+        SCReturnInt(-1);
     }
 
     int r = SSHParseData(ssh_state, ssh_header, input, input_len);

src/app-layer-ssl.c

@@ -976,6 +976,8 @@ static int SSLDecode(Flow *f, uint8_t direction, void *alstate, AppLayerParserSt
 
     if (input == NULL && AppLayerParserStateIssetFlag(pstate, APP_LAYER_PARSER_EOF)) {
         SCReturnInt(1);
+    } else if (input == NULL || input_len == 0) {
+        SCReturnInt(-1);
     }
 
     if (direction == 0)