https://bugs.gentoo.org/939446
https://sourceware.org/PR32164
https://sourceware.org/git/?p=glibc.git;a=commit;h=7073164add3b874cf0c19ca0fb84236f6bb0985d

From 7073164add3b874cf0c19ca0fb84236f6bb0985d Mon Sep 17 00:00:00 2001
From: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date: Tue, 3 Sep 2024 14:58:33 -0400
Subject: [PATCH] libio: Attempt wide backup free only for non-legacy code

_wide_data and _mode are not available in legacy code, so do not attempt
to free the wide backup buffer in legacy code.

Resolves: BZ #32137 and BZ #27821

Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
(cherry picked from commit ae4d44b1d501421ad9a3af95279b8f4d1546f1ce)
--- a/libio/genops.c
+++ b/libio/genops.c
@@ -819,7 +819,7 @@ _IO_unbuffer_all (void)
       /* Free up the backup area if it was ever allocated.  */
       if (_IO_have_backup (fp))
 	_IO_free_backup_area (fp);
-      if (fp->_mode > 0 && _IO_have_wbackup (fp))
+      if (!legacy && fp->_mode > 0 && _IO_have_wbackup (fp))
 	_IO_free_wbackup_area (fp);
 
       if (! (fp->_flags & _IO_UNBUFFERED)
-- 
2.43.5