localed: fix invalid free after shifting pointers using strstrip

After manually editing /etc/locale.gen, calling localectl set-locale
sometimes fails. When it fails, the systemd journal shows:
systemd-localed: free() / invalid pointer.

It turned out that it only fails if some of the uncommented lines in
/etc/locale.gen have leading spaces, as in:

  * C.UTF-8       <= OK
  * en_US.UTF-8   <= OK
  *  fr_FR.UTF-8  <= NOK

After parsing a line from /etc/locale.gen, we use strstrip() to obtain
the "trimmed" line (without leading or trailing spaces).

However, we store the result of strstrip() in the original pointer
containing the untrimmed line. This pointer is later passed to free
(this is done automatically using _cleanup_free_).

This is a problem because if any leading space is present, the pointer
will essentially be shifted from its original value. This will result in
an invalid free upon cleanup.

The same issue is present in the locale_gen_locale_supported function.

Fixed by storing the result of strstrip() in a different pointer.

diff --git a/src/locale/localed-util.c b/src/locale/localed-util.c
index 8ad5256ad9d472fb38acc966e67b35adb22e8858..5247d139eb7ea9d64766bbad68a7b697ecbecc1a 100644 (file)
--- a/src/locale/localed-util.c
+++ b/src/locale/localed-util.c
@@ -948,6 +948,7 @@ static int locale_gen_locale_supported(const char *locale_entry) {
 
         for (;;) {
                 _cleanup_free_ char *line = NULL;
+                char *l;
 
                 r = read_line(f, LONG_LINE_MAX, &line);
                 if (r < 0)
@@ -955,8 +956,8 @@ static int locale_gen_locale_supported(const char *locale_entry) {
                 if (r == 0)
                         return 0;
 
-                line = strstrip(line);
-                if (strcaseeq_ptr(line, locale_entry))
+                l = strstrip(line);
+                if (strcaseeq_ptr(l, locale_entry))
                         return 1;
         }
 }
@@ -1034,14 +1035,13 @@ int locale_gen_enable_locale(const char *locale) {
                                 continue;
                         }
 
-                        line = strstrip(line);
-                        if (isempty(line)) {
+                        line_locale = strstrip(line);
+                        if (isempty(line_locale)) {
                                 fputc('\n', fw);
                                 first_line = false;
                                 continue;
                         }
 
-                        line_locale = line;
                         if (line_locale[0] == '#')
                                 line_locale = strstrip(line_locale + 1);
                         else if (strcaseeq_ptr(line_locale, locale_entry))