From 79b2667d1eb06c6503c22f2f323c1c574ac5917b Mon Sep 17 00:00:00 2001 From: Joe Simmons-Talbott Date: Tue, 23 May 2023 15:41:29 -0400 Subject: time: strftime_l: Avoid an unbounded alloca. Avoid possible stack overflow by removing alloca() and converting to wide characters within the buffer. Suggested-by: Paul Eggert --- time/strftime_l.c | 39 +++++++++++++++++++++++++-------------- 1 file changed, 25 insertions(+), 14 deletions(-) (limited to 'time') diff --git a/time/strftime_l.c b/time/strftime_l.c index 402c6c4111..3901bd79da 100644 --- a/time/strftime_l.c +++ b/time/strftime_l.c @@ -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); -- cgit 1.4.1