modname_normalize: fix const and buffer overflow.

"buf[NAME_MAX] = value" is invalid since it would access the byte
right after the array.

Also fix the const of modname, do not mess with it to avoid mistakes.

diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
index 401daaa..b3b5430 100644 (file)
--- a/libkmod/libkmod-module.c
+++ b/libkmod/libkmod-module.c
@@ -53,29 +53,26 @@ struct kmod_module {
        char name[];
 };
 
-static inline char *modname_normalize(char *modname, char buf[NAME_MAX],
+static inline char *modname_normalize(const char *modname, char buf[NAME_MAX],
                                                                size_t *len)
 {
-       char *c;
        size_t s;
 
-       if (buf) {
-               buf[NAME_MAX] = '\0';
-               modname = strncpy(buf, modname, NAME_MAX - 1);
-       }
-
-       for (c = modname, s = 0; *c != '\0' && *c != '.'; c++) {
-               if (*c == '-')
-                       *c = '_';
-               s++;
+       for (s = 0; s < NAME_MAX - 1; s++) {
+               const char c = modname[s];
+               if (c == '-')
+                       buf[s] = '_';
+               else if (c == '\0' || c == '.')
+                       break;
+               else
+                       buf[s] = c;
        }
+       buf[s] = '\0';
 
        if (len)
                *len = s;
 
-       *c = '\0';
-
-       return modname;
+       return buf;
 }
 
 static char *path_to_modname(const char *path, char buf[NAME_MAX], size_t *len)
@@ -111,7 +108,8 @@ int kmod_module_parse_depline(struct kmod_module *mod, char *line)
 
        for (p = strtok_r(p, " \t", &saveptr); p != NULL;
                                        p = strtok_r(NULL, " \t", &saveptr)) {
-               const char *modname = path_to_modname(p, NULL, NULL);
+               char buf[NAME_MAX];
+               const char *modname = path_to_modname(p, buf, NULL);
                struct kmod_module *depmod;
 
                err = kmod_module_new_from_name(ctx, modname, &depmod);
@@ -149,7 +147,7 @@ KMOD_EXPORT int kmod_module_new_from_name(struct kmod_ctx *ctx,
        if (ctx == NULL || name == NULL)
                return -ENOENT;
 
-       modname_normalize((char *)name, name_norm, &namelen);
+       modname_normalize(name, name_norm, &namelen);
 
        m = kmod_pool_get_module(ctx, name_norm);
        if (m != NULL) {