libxl: fix -Werror=stringop-truncation in libxl__prepare_sockaddr_un

In file included from /usr/include/string.h:495,
                 from libxl_internal.h:38,
                 from libxl_utils.c:20:
In function 'strncpy',
    inlined from 'libxl__prepare_sockaddr_un' at libxl_utils.c:1262:5:
/usr/include/bits/string_fortified.h:106:10: error: '__builtin_strncpy' specified bound 108 equals destination size [-Werror=stringop-truncation]
  106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Reviewed-by: Ian Jackson <ian.jackson@eu.citrix.com>
(cherry picked from commit fff1b7f50e75ad9535c86f3fcf425b4945c50a1c)

diff --git a/tools/libxl/libxl_utils.c b/tools/libxl/libxl_utils.c
index f360f5e228e17a92c5c6222315cea286727f79c6..b039143b8aef902725f732d54d3d804853ad3cd4 100644 (file)
--- a/tools/libxl/libxl_utils.c
+++ b/tools/libxl/libxl_utils.c
@@ -1252,14 +1252,14 @@ int libxl__prepare_sockaddr_un(libxl__gc *gc,
                                struct sockaddr_un *un, const char *path,
                                const char *what)
 {
-    if (sizeof(un->sun_path) <= strlen(path)) {
+    if (sizeof(un->sun_path) - 1 <= strlen(path)) {
         LOG(ERROR, "UNIX socket path '%s' is too long for %s", path, what);
-        LOG(DEBUG, "Path must be less than %zu bytes", sizeof(un->sun_path));
+        LOG(DEBUG, "Path must be less than %zu bytes", sizeof(un->sun_path) - 1);
         return ERROR_INVAL;
     }
     memset(un, 0, sizeof(struct sockaddr_un));
     un->sun_family = AF_UNIX;
-    strncpy(un->sun_path, path, sizeof(un->sun_path));
+    strncpy(un->sun_path, path, sizeof(un->sun_path) - 1);
     return 0;
 }