time: strftime_l: Avoid an unbounded alloca.
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Commit Message
Avoid possible stack overflow by removing alloca() and converting to
wide characters within the buffer.
Suggested-by: Paul Eggert <eggert@cs.ucla.edu>
---
Supersedes: https://sourceware.org/pipermail/libc-alpha/2023-May/147996.html
time/strftime_l.c | 39 +++++++++++++++++++++++++--------------
1 file changed, 25 insertions(+), 14 deletions(-)
Comments
On 22/05/23 15:32, Joe Simmons-Talbott via Libc-alpha wrote:
> Avoid possible stack overflow by removing alloca() and converting to
> wide characters within the buffer.
>
> Suggested-by: Paul Eggert <eggert@cs.ucla.edu>
> ---
> Supersedes: https://sourceware.org/pipermail/libc-alpha/2023-May/147996.html
> time/strftime_l.c | 39 +++++++++++++++++++++++++--------------
> 1 file changed, 25 insertions(+), 14 deletions(-)
>
> diff --git a/time/strftime_l.c b/time/strftime_l.c
> index 402c6c4111..bb8e9e7f25 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);
This triggers a local PLT failure:
$ cat elf/check-localplt.out
Extra PLT reference: libc.so: wmemmove
I am not sure why it not caught by the buildbots. The rest of the patch looks
ok.
> + wchar_t wc = pad == L_('0') || pad == L_('+') ? L'0' : L' ';
> + wmemset (p, wc, delta);
> + }
> + p += incr;
> + }
> + i += incr;
> }
> #else
> cpy (strlen (zone), zone);
On Tue, May 23, 2023 at 04:11:05PM -0300, Adhemerval Zanella Netto wrote:
>
>
> On 22/05/23 15:32, Joe Simmons-Talbott via Libc-alpha wrote:
> > Avoid possible stack overflow by removing alloca() and converting to
> > wide characters within the buffer.
> >
> > Suggested-by: Paul Eggert <eggert@cs.ucla.edu>
> > ---
> > Supersedes: https://sourceware.org/pipermail/libc-alpha/2023-May/147996.html
> > time/strftime_l.c | 39 +++++++++++++++++++++++++--------------
> > 1 file changed, 25 insertions(+), 14 deletions(-)
> >
> > diff --git a/time/strftime_l.c b/time/strftime_l.c
> > index 402c6c4111..bb8e9e7f25 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);
>
>
> This triggers a local PLT failure:
>
> $ cat elf/check-localplt.out
> Extra PLT reference: libc.so: wmemmove
Thanks for catching that. Should be fixed in v2.
Thanks,
Joe
@@ -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);