$ gdb --args pwck
[...]
(gdb) run
Program received signal SIGSEGV, Segmentation fault.
___fprintf_chk (fp=0x0, flag=flag@entry=1, format=format@entry=0x55555555dc21 "%s: Permission denied.\n")
    at fprintf_chk.c:30
30      _IO_acquire_lock_clear_flags2 (fp);

(gdb) f 2
#2  commonio_lock (db=0x5555557605e0 <passwd_db>) at commonio.c:474
474                (void) fprintf (shadow_logfd, "%s: Permission denied.\n",
(gdb) p shadow_logfd 
$1 = (FILE *) 0x0

commit d8e54618feea201987c1f3cb402ed50d1d8b604f
Author: Iker Pedrosa <ipedrosa@redhat.com>
Date:   Mon Nov 15 12:40:15 2021 +0100

    pwck: fix segfault when calling fprintf()
    
    As shadow_logfd variable is not set at the beginning of the program if
    something fails and fprintf() is called a segmentation fault happens.
    
    Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2021339
    
    Signed-off-by: Iker Pedrosa <ipedrosa@redhat.com>
---
 src/pwck.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/pwck.c b/src/pwck.c
index 4248944a..4ce86af2 100644
--- a/src/pwck.c
+++ b/src/pwck.c
@@ -857,6 +857,7 @@ int main (int argc, char **argv)
         * Get my name so that I can use it to report errors.
         */
        Prog = Basename (argv[0]);
+       shadow_logfd = stderr;
 
        (void) setlocale (LC_ALL, "");
        (void) bindtextdomain (PACKAGE, LOCALEDIR);