charset: fix mm_charset_get_encoded_len

The while loop in mm_charset_get_encoded_len() iterates through each
valid UTF-8 encoded character in the given NULL-terminated UTF-8 string.
It uses g_utf8_find_next_char() to find the position of the next
character. In case, g_utf8_find_next_char() returns NULL, it tries to
find the end (i.e. the NULL character) of the string.

This patch fixes the following issues in the while loop:

1. The loop uses both 'next' and 'end' to track the position of the next
   character in the string.

   When g_utf8_find_next_char() returns a non-NULL value, 'next' is
   essentially the same as 'end'.

   When g_utf8_find_next_char() returns NULL, 'next' remains NULL while
   'end' is adjusted to track the end of the string (but is done
   incorrectly as described in #2). After the 'p = next' assignment, the
   'while (*p)' check results in a NULL dereference. 'p' should thus be
   set to 'end' instead of 'next'.

   'next' is thus redundant and can be removed.

2. When g_utf8_find_next_char() returns NULL and 'end' is adjusted to
   track the end of string, the 'while (*end++)' loop stops when finding
   the NULL character, but 'end' is advanced past the NULL character.
   After the 'p = end' assignment, the 'while (*p)' check results in a
   dereference of out-of-bounds pointer.

   'while (*++end)' should be used instead given that 'p' doesn't point
   to a NULL character when 'end = p' happens. 'end' will be updated to
   point to the NULL character. After the 'p = end' assignment (fixed in
   #1), the 'while (*p)' check will properly stop the loop.

0 files changed, 0 insertions, 0 deletions