| Message ID | 20230522183245.4161004-1-josimmon@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | time: strftime_l: Avoid an unbounded alloca. | expand |
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
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); + wchar_t wc = pad == L_('0') || pad == L_('+') ? L'0' : L' '; + wmemset (p, wc, delta); + } + p += incr; + } + i += incr; } #else cpy (strlen (zone), zone);