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libc/locale: Fix races between localeconv(3) and setlocale(3)

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Each locale embeds a lazily initialized lconv which is populated by
localeconv(3) and localeconv_l(3).  When setlocale(3) updates the global
locale, the lconv needs to be (lazily) reinitialized.  To signal this,
we set flag variables in the locale structure.  There are two problems:

- The flags are set before the locale is fully updated, so a concurrent
  localeconv() call can observe partially initialized locale data.
- No barriers ensure that localeconv() observes a fully initialized
  locale if a flag is set.

So, move the flag update appropriately, and use acq/rel barriers to
provide some synchronization.  Note that this is inadequate in the face
of multiple concurrent calls to setlocale(3), but this is not expected
to work regardless.

Thanks to Henry Hu <henry.hu.sh@gmail.com> for providing a test case
demonstrating the race.

PR:		258360
MFC after:	3 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D31899
This commit is contained in:
Mark Johnston 2021-09-17 10:44:23 -04:00
parent deef4b8ce8
commit 7eb138a9e5
3 changed files with 8 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
lib/libc/locale/lmonetary.c
View File

@ -107,8 +107,6 @@ monetary_load_locale_l(struct xlocale_monetary *loc, int *using_locale,
&loc->buffer, "LC_MONETARY",
LCMONETARY_SIZE_FULL, LCMONETARY_SIZE_MIN,
(const char **)l);
if (ret != _LDP_ERROR)
*changed = 1;
if (ret == _LDP_LOADED) {
l->mon_grouping =
__fix_locale_grouping_str(l->mon_grouping);
@ -146,6 +144,8 @@ monetary_load_locale_l(struct xlocale_monetary *loc, int *using_locale,
M_ASSIGN_ICHAR(p_sign_posn);
M_ASSIGN_ICHAR(n_sign_posn);
}
if (ret != _LDP_ERROR)
atomic_store_rel_int(changed, 1);
return (ret);
}
int

4
lib/libc/locale/lnumeric.c
View File

@ -73,8 +73,6 @@ numeric_load_locale(struct xlocale_numeric *loc, int *using_locale, int *changed
&loc->buffer, "LC_NUMERIC",
LCNUMERIC_SIZE, LCNUMERIC_SIZE,
(const char**)l);
if (ret != _LDP_ERROR)
*changed= 1;
if (ret == _LDP_LOADED) {
/* Can't be empty according to C99 */
if (*l->decimal_point == '\0')
@ -83,6 +81,8 @@ numeric_load_locale(struct xlocale_numeric *loc, int *using_locale, int *changed
l->grouping =
__fix_locale_grouping_str(l->grouping);
}
if (ret != _LDP_ERROR)
atomic_store_rel_int(changed, 1);
return (ret);
}

8
lib/libc/locale/localeconv.c
View File

@ -65,7 +65,7 @@ localeconv_l(locale_t loc)
FIX_LOCALE(loc);
struct lconv *ret = &loc->lconv;
if (loc->monetary_locale_changed) {
if (atomic_load_acq_int(&loc->monetary_locale_changed) != 0) {
/* LC_MONETARY part */
struct lc_monetary_T * mptr;
@ -94,10 +94,10 @@ localeconv_l(locale_t loc)
M_ASSIGN_CHAR(int_n_sep_by_space);
M_ASSIGN_CHAR(int_p_sign_posn);
M_ASSIGN_CHAR(int_n_sign_posn);
loc->monetary_locale_changed = 0;
atomic_store_int(&loc->monetary_locale_changed, 0);
}
if (loc->numeric_locale_changed) {
if (atomic_load_acq_int(&loc->numeric_locale_changed) != 0) {
/* LC_NUMERIC part */
struct lc_numeric_T * nptr;
@ -107,7 +107,7 @@ localeconv_l(locale_t loc)
N_ASSIGN_STR(decimal_point);
N_ASSIGN_STR(thousands_sep);
N_ASSIGN_STR(grouping);
loc->numeric_locale_changed = 0;
atomic_store_int(&loc->numeric_locale_changed, 0);
}
return ret;