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bound the trailing hex read in my_mb_wc_filename #5187

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bound the trailing hex read in my_mb_wc_filename #5187

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2 changes: 1 addition & 1 deletion strings/ctype-utf8.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2561,7 +2561,7 @@ my_mb_wc_filename(CHARSET_INFO *cs __attribute__((unused)),
(byte2= hexlo(byte2)) >= 0)
{
int byte3= hexlo(s[3]);
int byte4= hexlo(s[3] ? s[4] : 0);
int byte4= hexlo((s[3] && s + 4 < e) ? s[4] : 0);
if (byte3 >=0 && byte4 >=0)
{
*pwc= (byte1 << 12) + (byte2 << 8) + (byte3 << 4) + byte4;
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23 changes: 22 additions & 1 deletion unittest/strings/strings-t.c
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Expand Up @@ -1704,13 +1704,30 @@ test_strnncollsp_char()
}


/*
my_mb_wc_filename() decodes a 5-byte '@HHHH' escape but only checked that
4 bytes were available before reading the 4th hex digit at s[4], one byte
past the supplied end pointer. "@000" is such a truncated escape ('0','0'
has no entry in the 3-byte table, so it reaches the hex branch). Passing
end= buf + 4 must not consume the byte at buf[4].
*/
static int test_mb_wc_filename_truncated()
{
CHARSET_INFO *cs= &my_charset_filename;
uchar buf[5]= {'@', '0', '0', '0', '1'};
my_wc_t wc= 0;
int rc= my_ci_mb_wc(cs, &wc, buf, buf + 4);
return rc != MY_CS_ILSEQ;
}
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@gemini-code-assist gemini-code-assist Bot Jun 5, 2026

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medium

Returning the actual return value of my_ci_mb_wc rather than a boolean mapping makes the test more direct and easier to understand. We can then assert the expected error code (MY_CS_ILSEQ) directly in the test runner.

static int test_mb_wc_filename_truncated()
{
  CHARSET_INFO *cs= &my_charset_filename;
  uchar buf[5]= {'@', '0', '0', '0', '1'};
  my_wc_t wc= 0;
  return my_ci_mb_wc(cs, &wc, buf, buf + 4);
}



int main(int ac, char **av)
{
size_t i, failed= 0;

MY_INIT(av[0]);

plan(4);
plan(5);
diag("Testing my_like_range_xxx() functions");

for (i= 0; i < array_elements(charset_list); i++)
Expand All @@ -1736,6 +1753,10 @@ int main(int ac, char **av)
failed= test_strnncollsp_char();
ok(failed == 0, "Testing cs->coll->strnncollsp_char()");

diag("Testing my_charset_filename mb_wc end-pointer bounds");
ok(test_mb_wc_filename_truncated() == 0,
"filename decoder does not read past the end pointer");
Comment on lines +1757 to +1758
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@gemini-code-assist gemini-code-assist Bot Jun 5, 2026

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medium

Asserting the expected error code (MY_CS_ILSEQ) directly is more idiomatic and provides clearer test output if the assertion fails.

  ok(test_mb_wc_filename_truncated() == MY_CS_ILSEQ,
     "filename decoder does not read past the end pointer");


my_end(0);

return exit_status();
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