rework login and discovery code to avoid strlen beyond end of data

Checking for the presence of the NUL character should be done
without accessing beyond the PDU datain.  Use memchr instead
of strlen, and compute the length only if a NUL character is
actually there.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

lib/discovery.c

@@ -118,25 +118,34 @@ iscsi_process_text_reply(struct iscsi_context *iscsi, struct iscsi_pdu *pdu,
 			      pdu->private_data);
 		return -1;
 	}
+	if (size == 0) {
+		iscsi_set_error(iscsi, "size == 0 when parsing "
+				"discovery data");
+		pdu->callback(iscsi, SCSI_STATUS_ERROR, NULL,
+			      pdu->private_data);
+		return -1;
+	}
 
-	while (size > 0) {
+	do {
+		unsigned char *end;
 		int len;
 
-		len = strlen((char *)ptr);
+		end = memchr(ptr, 0, size);
-
+		if (end == NULL) {
-		if (len == 0) {
+			iscsi_set_error(iscsi, "NUL not found after offset %ld "
-			break;
+					"when parsing discovery data",
-		}
+					ptr - in->data);
-
-		if (len > size) {
-			iscsi_set_error(iscsi, "len > size when parsing "
-					"discovery data %d>%d", len, size);
 			pdu->callback(iscsi, SCSI_STATUS_ERROR, NULL,
 				      pdu->private_data);
 			iscsi_free_discovery_addresses(iscsi, targets);
 			return -1;
 		}
 
+		len = end - ptr;
+		if (len == 0) {
+			break;
+		}
+
 		/* parse the strings */
 		if (!strncmp((char *)ptr, "TargetName=", 11)) {
 			struct iscsi_discovery_address *target;
@@ -187,7 +196,7 @@ iscsi_process_text_reply(struct iscsi_context *iscsi, struct iscsi_pdu *pdu,
 
 		ptr  += len + 1;
 		size -= len + 1;
-	}
+	} while (size > 0);
 
 	pdu->callback(iscsi, SCSI_STATUS_GOOD, targets, pdu->private_data);
 	iscsi_free_discovery_addresses(iscsi, targets);

lib/login.c

@@ -981,30 +981,40 @@ iscsi_process_login_reply(struct iscsi_context *iscsi, struct iscsi_pdu *pdu,
 	if (iscsi_serial32_compare(expcmdsn, iscsi->expcmdsn) > 0) {
 		iscsi->expcmdsn = expcmdsn;
 	}
-	
+
+	if (size == 0) {
+	       iscsi_set_error(iscsi, "size == 0 when parsing "
+			       "login data");
+	       pdu->callback(iscsi, SCSI_STATUS_ERROR, NULL,
+			     pdu->private_data);
+	       return -1;
+	}
+
 	/* XXX here we should parse the data returned in case the target
 	 * renegotiated some some parameters.
 	 *  we should also do proper handshaking if the target is not yet
 	 * prepared to transition to the next stage
 	 */
 
-	while (size > 0) {
+	do {
+		char *end;
 		int len;
 
-		len = strlen(ptr);
+		end = memchr(ptr, 0, size);
-
+		if (end == NULL) {
-		if (len == 0) {
+			iscsi_set_error(iscsi, "NUL not found after offset %ld "
-			break;
+					"when parsing login data",
-		}
+					(unsigned char *)ptr - in->data);
-
-		if (len > size) {
-			iscsi_set_error(iscsi, "len > size when parsing "
-					"login data %d>%d", len, size);
 			pdu->callback(iscsi, SCSI_STATUS_ERROR, NULL,
 				      pdu->private_data);
 			return -1;
 		}
 
+		len = end - ptr;
+		if (len == 0) {
+			break;
+		}
+
 		/* parse the strings */
 		if (!strncmp(ptr, "TargetAddress=", 14)) {
 			strncpy(iscsi->target_address,ptr+14,MAX_STRING_SIZE);
@@ -1077,7 +1087,7 @@ iscsi_process_login_reply(struct iscsi_context *iscsi, struct iscsi_pdu *pdu,
 
 		ptr  += len + 1;
 		size -= len + 1;
-	}
+	} while (size > 0);
 
 	if (status == SCSI_STATUS_REDIRECT && iscsi->target_address[0]) {
 		ISCSI_LOG(iscsi, 2, "target requests redirect to %s",iscsi->target_address);