How is this related to bug 1206462?

I cannot reproduce this.  I have this line in /etc/passwd:

testuser1:x:1001:1001:12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234:/home/testuser1:/bin/bash

And:

$ getent passwd testuser1 | wc -c
1023

And the user is able to log in after setting a password (with OpenSSH password authentication).

My guess is that the customer tries to log on over a TTY or via telnetd.  In this case, the system log should contain an error message like this one:

Dec 11 05:35:09 localhost login[28294]: Invalid user name "testuser1" in main:1229. Abort

This refers to login-utils/login.c in util-linux.  The error reflects a failure of the get_passwd_entry function, which does this:

	struct passwd *res = NULL;
	size_t sz = 16384;
	int x;

	if (!pwdbuf || !username)
		return NULL;

#ifdef _SC_GETPW_R_SIZE_MAX
	{
		long xsz = sysconf(_SC_GETPW_R_SIZE_MAX);
		if (xsz > 0)
			sz = (size_t) xsz;
	}
#endif
	*pwdbuf = xrealloc(*pwdbuf, sz);

	x = getpwnam_r(username, pwd, *pwdbuf, sz, &res);

_SC_GETPW_R_SIZE_MAX is misnamed, it is a recommended starting value, not an upper bound.  But the code in util-linux does not retry with a larger buffer, as it is reqired.  See the getpwnam_r manual page for details.

> _SC_GETPW_R_SIZE_MAX is misnamed, it is a recommended starting value, not an upper bound.  

Your guess might be right.


  $ cat /etc/redhat-release 
  Red Hat Enterprise Linux Server release 7.2 (Maipo)

  $ rpm -q glibc
  glibc-2.17-106.el7_2.1.x86_64

  $ cat test_sysconf.c
 
  #include<stdio.h>
  #include<unistd.h>
  
  int main(){
    size_t sz = 16384;
    long xsz = sysconf(_SC_GETPW_R_SIZE_MAX);
    if(xsz > 0){
      sz = (size_t)xsz;
    }
    printf("%d %d\n", sz, xsz );
    return 0;
  }

  $ gcc -o test_sysconf test_sysconf.c
  $  ./test_sysconf
  1024 1024

Please, fix getpwnam man page, because EXAMPLE section suggests SC_GETPW_R_SIZE_MAX as optimal buffer size...

Fixed by upstream commit f7ac9e71b18fa7314151f2ab65ee0bdd2ea89c07.

The patch hardcodes 16K buffer size, not sure if we have something more elegant...

(In reply to Karel Zak from comment #6)
> Fixed by upstream commit f7ac9e71b18fa7314151f2ab65ee0bdd2ea89c07.
> 
> The patch hardcodes 16K buffer size, not sure if we have something more
> elegant...

The recommended way is to keep retrying with a larger buffer size, doubling it every time.  The API is somewhat on the bizarre side, but it's how it was standardized in POSIX.

This bug was accidentally moved from POST to MODIFIED via an error in automation, please see mmccune with any questions

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://rhn.redhat.com/errata/RHSA-2016-2605.html