[review v2] wcsrtombs: Do not call wcsnlen on input with wrong length [BZ #23711]

["Carlos O'Donell (Code Review)" <gerrit at gnutoolchain-gerrit dot osci dot io>]

Carlos O'Donell has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/glibc/+/445
......................................................................


Patch Set 2: Code-Review+2

(1 comment)

OK for master.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

| --- wcsmbs/wcsrtombs.c
| +++ wcsmbs/wcsrtombs.c
| @@ -98,17 +98,29 @@ #endif
|      }
|    else
|      {
| -      /* This code is based on the safe assumption that all internal
| -	 multi-byte encodings use the NUL byte only to mark the end
| -	 of the string.  */
| -      const wchar_t *srcend = *src + __wcsnlen (*src, len) + 1;
|        size_t dummy;
|  
| +      /* This code is based on the safe assumption that all internal
| +	 multi-byte encodings use the NUL byte only to mark the end of
| +	 the string.  It also assumes that every wide character
| +	 produces at least one byte of output.  This is true for all
| +	 supported locales, including the very special case of the
| +	 Big5 character set.  But custom locales (e.g., for TSCII)
| +	 might not have this property.
| +
| +	 Do not use wcsnlen because the input may not be an array of
| +	 len wchar_t elements, given that len is the length of the
| +	 *destination* array.  */
| +      const wchar_t *srcend = *src;
| +      while (srcend < *src + len && *srcend != L'\0')
| +	++srcend;
| +      ++srcend;

PS2, Line 117:

OK. This looks good to me. We scan src looking for L'\0' rather than
using wcsnlen which is undefined because len may be longer than src's
real length.

| +
|        data.__outbuf = (unsigned char *) dst;
|        data.__outbufend = (unsigned char *) dst + len;
|  
|        status = DL_CALL_FCT (fct, (tomb, &data, (const unsigned char **) src,
|  				  (const unsigned char *) srcend, NULL,
|  				  &dummy, 0, 1));
|  
|        /* Count the number of bytes.  */

-- 
Gerrit-Project: glibc
Gerrit-Branch: master
Gerrit-Change-Id: I5b28fb36c8d224cf69910fb436ff76bff8f129f6
Gerrit-Change-Number: 445
Gerrit-PatchSet: 2
Gerrit-Owner: Florian Weimer <fweimer@redhat.com>
Gerrit-Reviewer: Carlos O'Donell <carlos@redhat.com>
Gerrit-Reviewer: Florian Weimer <fweimer@redhat.com>
Gerrit-Comment-Date: Wed, 27 Nov 2019 19:12:38 +0000
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