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* [PATCH] newlocale: fix crash when trying to write to __C_locale
@ 2022-08-11 17:35 Corinna Vinschen
  0 siblings, 0 replies; only message in thread
From: Corinna Vinschen @ 2022-08-11 17:35 UTC (permalink / raw)
  To: cygwin-patches

This simple testcase:

  locale_t st = newlocale(LC_ALL_MASK, "C", (locale_t)0);
  locale_t st2 = newlocale(LC_CTYPE_MASK, "en_US.UTF-8", st);

is sufficient to reproduce a crash in _newlocale_r.  After the first call
to newlocale, `st' points to __C_locale, which is const.  When using `st'
as locale base in the second call, _newlocale_r tries to set pointers
inside base to NULL.  This is bad if base is __C_locale, obviously.

Add a test to avoid trying to overwrite pointer values inside base if
base is __C_locale.

Signed-off-by: Corinna Vinschen <>
 newlib/libc/locale/newlocale.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/newlib/libc/locale/newlocale.c b/newlib/libc/locale/newlocale.c
index 0789d5fd95ec..08f29dbcc0c1 100644
--- a/newlib/libc/locale/newlocale.c
+++ b/newlib/libc/locale/newlocale.c
@@ -188,7 +188,8 @@ _newlocale_r (struct _reent *p, int category_mask, const char *locale,
 	if (tmp_locale.lc_cat[i].buf == (const void *) -1)
 	    tmp_locale.lc_cat[i].buf = base->lc_cat[i].buf;
-	    base->lc_cat[i].ptr = base->lc_cat[i].buf = NULL;
+	    if (base != __get_C_locale ())
+	      base->lc_cat[i].ptr = base->lc_cat[i].buf = NULL;
 #endif /* __HAVE_LOCALE_INFO__ */
       _freelocale_r (p, base);

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2022-08-11 17:35 [PATCH] newlocale: fix crash when trying to write to __C_locale Corinna Vinschen

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