data_management: create_node asan fix

When executing on /usr/bin or /usr/lib it sometimes happened after
a few hundred files, that even if source and target were arrays of
type char[256] memcpy would be noted as a heap buffer overflow.

Switching to strnlen(fname,256) and dst[255]='\0'; to be flexible
and getting rid of the asan error.

1 files changed, 16 insertions, 5 deletions

diff --git a/src/data_management.c b/src/data_management.c
index d4cf76c..ff2b3a9 100644
--- a/src/data_management.c
+++ b/src/data_management.c
@@ -21,6 +21,12 @@
 
 inline struct list_node *create_node(char *fname, struct stat *ln_stat) {
     struct list_node *node = NULL;
+    size_t length = 0;
+#ifdef DEBUGBUILD
+    static size_t count = 0;
+
+    DBGTRC("DEBUG: Called fname '%s', attempting to create node #%lu\n", fname, ++count);
+#endif
 
     if (fname == NULL || fname[0] == '\0') {
         LOGERR("ERROR: No valid filename given\n");
@@ -37,12 +43,17 @@ inline struct list_node *create_node(char *fname, struct stat *ln_stat) {
         return NULL;
     }
 
+    length = strnlen(fname,256);
+    if (length>255) {
+        LOGERR("ERROR: strnlen(\"%s\",256) == %lu, terminating with '\\0' at char[255].\n",
+                fname, length);
+        length = 255;
+    }
     node->next = NULL;
-    /* With strncpy and strict compiler options it complained. A file name
-     * can't be longer than 256 bytes, including the string terminating \0
-     * byte at the end. As the code no longer's in the same file...*/
-    memcpy(node->fname, fname, 255);
-    node->fname[255] = '\0';
+    memcpy(node->fname, fname, length);
+    if (node->fname[255] != '\0') {
+        node->fname[255] = '\0';
+    }
     memcpy(&(node->ln_stat), ln_stat, sizeof(struct stat));
     return node;
 }