mavlink: fix stack buffer overflow in log handler filepath parsing

- Size LogEntry.filepath to PX4_MAX_FILEPATH instead of hardcoded 60 bytes
- Add width specifier to sscanf calls to prevent buffer overflow
- Move platform defines from .cpp to .h for reuse
- Add static_assert to enforce scanf width < buffer size at compile time

Co-authored-by: Cavan O'Horo <cavan.ohoro@gmail.com>
Signed-off-by: Ramon Roche <mrpollo@gmail.com>

src/modules/mavlink/mavlink_log_handler.h

@@ -32,10 +32,24 @@
  ****************************************************************************/
 
 #pragma once
-
 #include <perf/perf_counter.h>
 #include "mavlink_bridge_header.h"
 
+#ifdef __PX4_NUTTX
+#define PX4LOG_REGULAR_FILE    DTYPE_FILE
+#define PX4LOG_DIRECTORY       DTYPE_DIRECTORY
+#define PX4_MAX_FILEPATH       CONFIG_PATH_MAX
+#define PX4_MAX_FILEPATH_SCANF 255
+#else
+#ifndef PATH_MAX
+#define PATH_MAX 1024 // maximum on macOS
+#endif
+#define PX4LOG_REGULAR_FILE    DT_REG
+#define PX4LOG_DIRECTORY       DT_DIR
+#define PX4_MAX_FILEPATH       PATH_MAX
+#define PX4_MAX_FILEPATH_SCANF 1023
+#endif
+
 class Mavlink;
 
 class MavlinkLogHandler
@@ -53,7 +67,7 @@ private:
 		uint32_t time_utc{};
 		uint32_t size_bytes{};
 		FILE *fp{nullptr};
-		char filepath[60];
+		char filepath[PX4_MAX_FILEPATH];
 		uint32_t offset{};
 	};