Re: [PATCH v2] net/tap-win32: Fix gcc 14 format truncation errors

[Bernhard Beschow]

Am 8. Oktober 2024 20:28:42 UTC schrieb Bernhard Beschow <shentey@gmail.com>:
>The patch fixes the following errors generated by GCC 14.2:
>
>../src/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);
>      |                                       ~~~~~~~~~
>
>../src/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);
>      |              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>../src/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);
>      |                                ~~~~~~~~~
>
>../src/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);
>      |                   ~~~~~~~~~~~~~~~~~~~~~~~
>
>../src/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,
>      |               ~~~~~~~~~~~
>../src/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: Bernhard Beschow <shentey@gmail.com>
>Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2607
>Cc: qemu-stable@nongnu.org
>
>--
>
>This patch was just compile-tested (which fixes my issue). Testing TAP
>networking under Windows apparently requires extra drivers which I don't want 
>to
>install (not my computer). So it would be nice if someone could give this patch
>a test ride. Thanks!

Ping. Patch is reviewed. Any testers or shall we just merge?

Best regards,
Bernhard

>
>Changes since v1:
>* Use g_autofree and g_strdup_printf() rather than fixed size arrays (Peter)
>---
> net/tap-win32.c | 15 ++++++---------
> 1 file changed, 6 insertions(+), 9 deletions(-)
>
>diff --git a/net/tap-win32.c b/net/tap-win32.c
>index 7edbd71633..671dee970f 100644
>--- a/net/tap-win32.c
>+++ b/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];
>+        g_autofree char *unit_string = NULL;
>         HKEY unit_key;
>         char component_id_string[] = "ComponentId";
>         char component_id[256];
>@@ -239,8 +239,7 @@ static int is_tap_win32_dev(const char *guid)
>             return FALSE;
>         }
> 
>-        snprintf (unit_string, sizeof(unit_string), "%s\\%s",
>-                  ADAPTER_KEY, enum_name);
>+        unit_string = g_strdup_printf("%s\\%s", ADAPTER_KEY, enum_name);
> 
>         status = RegOpenKeyEx(
>             HKEY_LOCAL_MACHINE,
>@@ -315,7 +314,7 @@ static int get_device_guid(
>     while (!stop)
>     {
>         char enum_name[256];
>-        char connection_string[256];
>+        g_autofree char *connection_string = NULL;
>         HKEY connection_key;
>         char name_data[256];
>         DWORD name_type;
>@@ -338,9 +337,7 @@ static int get_device_guid(
>             return -1;
>         }
> 
>-        snprintf(connection_string,
>-             sizeof(connection_string),
>-             "%s\\%s\\Connection",
>+        connection_string = g_strdup_printf("%s\\%s\\Connection",
>              NETWORK_CONNECTIONS_KEY, enum_name);
> 
>         status = RegOpenKeyEx(
>@@ -595,7 +592,7 @@ 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];
>+    g_autofree char *device_path = NULL;
>     char device_guid[0x100];
>     int rc;
>     HANDLE handle;
>@@ -617,7 +614,7 @@ static int tap_win32_open(tap_win32_overlapped_t **phandle,
>     if (rc)
>         return -1;
> 
>-    snprintf (device_path, sizeof(device_path), "%s%s%s",
>+    device_path = g_strdup_printf("%s%s%s",
>               USERMODEDEVICEDIR,
>               device_guid,
>               TAPSUFFIX);