tap-win32: fix format-truncation warning

Simply increase destination buffer size so truncation can't happen.

"cc" "-m64" "-Ilibcommon.a.p" "-Isubprojects/dtc/libfdt" "-I../subprojects/dtc/libfdt" "-ID:/a/_temp/msys64/mingw64/include/pixman-1" "-ID:/a/_temp/msys64/mingw64/include/glib-2.0" "-ID:/a/_temp/msys64/mingw64/lib/glib-2.0/include" "-ID:/a/_temp/msys64/mingw64/include/ncursesw" "-fdiagnostics-color=auto" "-Wall" "-Winvalid-pch" "-Werror" "-std=gnu11" "-O2" "-g" "-fstack-protector-strong" "-Wempty-body" "-Wendif-labels" "-Wexpansion-to-defined" "-Wformat-security" "-Wformat-y2k" "-Wignored-qualifiers" "-Wimplicit-fallthrough=2" "-Winit-self" "-Wmissing-format-attribute" "-Wmissing-prototypes" "-Wnested-externs" "-Wold-style-declaration" "-Wold-style-definition" "-Wredundant-decls" "-Wshadow=local" "-Wstrict-prototypes" "-Wtype-limits" "-Wundef" "-Wvla" "-Wwrite-strings" "-Wno-missing-include-dirs" "-Wno-psabi" "-Wno-shift-negative-value" "-iquote" "." "-iquote" "D:/a/qemu/qemu" "-iquote" "D:/a/qemu/qemu/include" "-iquote" "D:/a/qemu/qemu/host/include/x86_64" "-iquote" "D:/a/qemu/qemu/host/include/generic" "-iq
../net/tap-win32.c: In function 'tap_win32_open':
../net/tap-win32.c:343:19: error: '%s' directive output may be truncated writing up to 255 bytes into a region of size 176 [-Werror=format-truncation=]
  343 |              "%s\\%s\\Connection",
      |                   ^~
  344 |              NETWORK_CONNECTIONS_KEY, enum_name);
      |                                       ~~~~~~~~~
In function 'get_device_guid',
    inlined from 'tap_win32_open' at ../net/tap-win32.c:616:10:
../net/tap-win32.c:341:9: note: 'snprintf' output between 92 and 347 bytes into a destination of size 256
  341 |         snprintf(connection_string,
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
  342 |              sizeof(connection_string),
      |              ~~~~~~~~~~~~~~~~~~~~~~~~~~
  343 |              "%s\\%s\\Connection",
      |              ~~~~~~~~~~~~~~~~~~~~~
  344 |              NETWORK_CONNECTIONS_KEY, enum_name);
      |              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../net/tap-win32.c: In function 'tap_win32_open':
../net/tap-win32.c:242:58: error: '%s' directive output may be truncated writing up to 255 bytes into a region of size 178 [-Werror=format-truncation=]
  242 |         snprintf (unit_string, sizeof(unit_string), "%s\\%s",
      |                                                          ^~
  243 |                   ADAPTER_KEY, enum_name);
      |                                ~~~~~~~~~
In function 'is_tap_win32_dev',
    inlined from 'get_device_guid' at ../net/tap-win32.c:368:21,
    inlined from 'tap_win32_open' at ../net/tap-win32.c:616:10:
../net/tap-win32.c:242:9: note: 'snprintf' output between 79 and 334 bytes into a destination of size 256
  242 |         snprintf (unit_string, sizeof(unit_string), "%s\\%s",
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  243 |                   ADAPTER_KEY, enum_name);
      |                   ~~~~~~~~~~~~~~~~~~~~~~~
../net/tap-win32.c: In function 'tap_win32_open':
../net/tap-win32.c:620:52: error: '%s' directive output may be truncated writing up to 255 bytes into a region of size 245 [-Werror=format-truncation=]
  620 |     snprintf (device_path, sizeof(device_path), "%s%s%s",
      |                                                    ^~
  621 |               USERMODEDEVICEDIR,
  622 |               device_guid,
      |               ~~~~~~~~~~~
../net/tap-win32.c:620:5: note: 'snprintf' output between 16 and 271 bytes into a destination of size 256
  620 |     snprintf (device_path, sizeof(device_path), "%s%s%s",
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  621 |               USERMODEDEVICEDIR,
      |               ~~~~~~~~~~~~~~~~~~
  622 |               device_guid,
      |               ~~~~~~~~~~~~
  623 |               TAPSUFFIX);
      |               ~~~~~~~~~~

Signed-off-by: Pierrick Bouvier <[email protected]>

net/tap-win32.c

@@ -214,7 +214,7 @@ static int is_tap_win32_dev(const char *guid)
 
     for (;;) {
         char enum_name[256];
-        char unit_string[256];
+        char unit_string[512];
         HKEY unit_key;
         char component_id_string[] = "ComponentId";
         char component_id[256];
@@ -315,7 +315,7 @@ static int get_device_guid(
     while (!stop)
     {
         char enum_name[256];
-        char connection_string[256];
+        char connection_string[512];
         HKEY connection_key;
         char name_data[256];
         DWORD name_type;
@@ -595,7 +595,7 @@ static void tap_win32_free_buffer(tap_win32_overlapped_t *overlapped,
 static int tap_win32_open(tap_win32_overlapped_t **phandle,
                           const char *preferred_name)
 {
-    char device_path[256];
+    char device_path[512];
     char device_guid[0x100];
     int rc;
     HANDLE handle;