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Bug 1698015 - glibc: Calling getpwent after endpwent should not crash?
Summary: glibc: Calling getpwent after endpwent should not crash?
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: glibc
Version: 7.6
Hardware: All
OS: Linux
Target Milestone: rc
: ---
Assignee: DJ Delorie
QA Contact: qe-baseos-tools-bugs
Depends On:
Blocks: 1710258
TreeView+ depends on / blocked
Reported: 2019-04-09 12:52 UTC by Paulo Andrade
Modified: 2020-03-31 19:08 UTC (History)
8 users (show)

Fixed In Version: glibc-2.17-302.el7
Doc Type: No Doc Update
Doc Text:
Clone Of:
: 1747502 (view as bug list)
Last Closed: 2020-03-31 19:08:32 UTC
Target Upstream Version:

Attachments (Terms of Use)

System ID Private Priority Status Summary Last Updated
Red Hat Bugzilla 1213603 0 urgent CLOSED glibc: nss_db: get*ent crashes without preceding set*ent 2021-02-22 00:41:40 UTC
Red Hat Product Errata RHBA-2020:0989 0 None None None 2020-03-31 19:08:51 UTC
Sourceware 24695 0 P2 RESOLVED nss_db: calling getpwent after endpwent crashes 2020-05-22 16:48:10 UTC
Sourceware 24696 0 P2 RESOLVED endgrent() clobbers errno=ERRNO for 'group: db files' entry in /etc/nsswitch.conf 2020-05-22 16:48:10 UTC

Internal Links: 1213603 1747502

Description Paulo Andrade 2019-04-09 12:52:36 UTC
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++);

//    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);

  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?

Comment 2 Florian Weimer 2019-04-09 13:17:31 UTC
Confirmed.  This is distinct from bug 1213603.

Comment 9 Sergey Kolosov 2019-11-15 22:00:24 UTC
Verified with the reproducer

Comment 11 errata-xmlrpc 2020-03-31 19:08:32 UTC
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.


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