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time: strftime_l: Avoid an unbounded alloca.

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Avoid possible stack overflow by removing alloca() and converting to
wide characters within the buffer.

Suggested-by: Paul Eggert <eggert@cs.ucla.edu>
This commit is contained in:
Joe Simmons-Talbott 2023-05-23 15:41:29 -04:00 committed by Siddhesh Poyarekar
parent ed2f9dc942
commit 79b2667d1e
1 changed files with 25 additions and 14 deletions
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39
time/strftime_l.c
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@ -267,15 +267,6 @@ static const CHAR_T zeroes[16] = /* "0000000000000000" */
# undef __mbsrtowcs_l
# define __mbsrtowcs_l(d, s, l, st, loc) __mbsrtowcs (d, s, l, st)
# endif
# define widen(os, ws, l) \
{ \
mbstate_t __st; \
const char *__s = os; \
memset (&__st, '\0', sizeof (__st)); \
l = __mbsrtowcs_l (NULL, &__s, 0, &__st, loc); \
ws = alloca ((l + 1) * sizeof (wchar_t)); \
(void) __mbsrtowcs_l (ws, &__s, l, &__st, loc); \
}
#endif
@ -1342,11 +1333,31 @@ __strftime_internal (CHAR_T *s, size_t maxsize, const CHAR_T *format,
#ifdef COMPILE_WIDE
{
/* The zone string is always given in multibyte form. We have
to transform it first. */
wchar_t *wczone;
size_t len;
widen (zone, wczone, len);
cpy (len, wczone);
to convert it to wide character. */
size_t w = pad == L_('-') || width < 0 ? 0 : width;
char const *z = zone;
mbstate_t st = {0};
size_t len = __mbsrtowcs_l (p, &z, maxsize - i, &st, loc);
if (len == (size_t) -1)
return 0;
size_t incr = len < w ? w : len;
if (incr >= maxsize - i)
{
errno = ERANGE;
return 0;
}
if (p)
{
if (len < w)
{
size_t delta = w - len;
__wmemmove (p + delta, p, len);
wchar_t wc = pad == L_('0') || pad == L_('+') ? L'0' : L' ';
wmemset (p, wc, delta);
}
p += incr;
}
i += incr;
}
#else
cpy (strlen (zone), zone);