From 7eb138a9e53636366e615bdf04062fedc044bcea Mon Sep 17 00:00:00 2001 From: Mark Johnston Date: Fri, 17 Sep 2021 10:44:23 -0400 Subject: [PATCH] libc/locale: Fix races between localeconv(3) and setlocale(3) 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 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 --- lib/libc/locale/lmonetary.c | 4 ++-- lib/libc/locale/lnumeric.c | 4 ++-- lib/libc/locale/localeconv.c | 8 ++++---- 3 files changed, 8 insertions(+), 8 deletions(-) diff --git a/lib/libc/locale/lmonetary.c b/lib/libc/locale/lmonetary.c index 99800ae69922..b8b4e78c060b 100644 --- a/lib/libc/locale/lmonetary.c +++ b/lib/libc/locale/lmonetary.c @@ -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 diff --git a/lib/libc/locale/lnumeric.c b/lib/libc/locale/lnumeric.c index 046d1f1817dc..cc1daa3863e3 100644 --- a/lib/libc/locale/lnumeric.c +++ b/lib/libc/locale/lnumeric.c @@ -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); } diff --git a/lib/libc/locale/localeconv.c b/lib/libc/locale/localeconv.c index 641773944e32..130f93c178f4 100644 --- a/lib/libc/locale/localeconv.c +++ b/lib/libc/locale/localeconv.c @@ -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;