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To setup the problem, edit /etc/nsswith.conf and add 'db' first, for example
-passwd files sss
+passwd db files sss

  Then, this example program will crash if setpwent is not called:

"""
#include <stdio.h>
#include <sys/types.h>
#include <pwd.h>
#include <grp.h>

void main()
{
    int usercnt;
    int grpcnt;
    struct passwd *p;

    // setpwent();  not absolutely required but good practice
    p = getpwent();
    for(usercnt = 0; p; p = getpwent(), usercnt++);
    endpwent();

//    setpwent(); if uncomment it the code does not segfault
    p = getpwent();
    for(usercnt = 0; p; p = getpwent(), usercnt++) {
        printf("%s (%d)\tHOME %s\tSHELL %s\n", p->pw_name, p->pw_uid, p->pw_dir, p->pw_shell);
    }
    setpwent();
}
"""

  If not using passwd.db apparently the default behaviour is to have
endpwent to implicitly rewind, so, setpwent is somewhat useless other
than when using a database.

  Is the crash (due to reading past the end of the stream) expected?

Confirmed.  This is distinct from bug 1213603.

Verified with the reproducer

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2020:0989