Description of problem:

As an NFS client with home directories on mounted NFS share - If the NFS server exports the share with default root squashed, login cannot access the filesystem to check for the existence of .hushlogin file - login uses the file to determine if motd and last is shown/updated on login.

Version-Release number of selected component (if applicable):
Reported originally in util-linux-2.13-0.47.el5-x86_64 but problem exists in all versions of util-linux packages for RHEL5.

How reproducible:
100%

Steps to Reproduce:
1. Create a user on NFS server for example:
motdtest:x:3333:3333:None:/home/motdtest:/bin/bash

2. Export motdtest user's home directory:
/home/motdtest 10.0.0.1(rw)

3. service nfs start

4. Create a user on NFS client that uses mount poiny /nfs-home for home directory:
motdtest:x:3333:3333:None:/nfs-home:/bin/bash

5. Create entry in /etc/fstab on NFS client
10.0.0.2:/home/motdtest /nfs-home nfs nfsvers=3,hard,intr,tcp 0 0
mkdir /nfs-home

6. Mount the NFS export
mount /nfs-home

7. login at console on NFS client and create .hushlogin file :
touch .hushlogin

8. Logout and login again as motdtest user


Actual results:
The meesage of the day is displayed, and last is updated. 




Expected results:
The message of the day should be shown and last should not be updated.

Additional info:

strace attached to mingetty tty1 shows :

getuid()                                = 0
getegid()                               = 0
setregid(4294967295, 3333)              = 0
setreuid(0, 3333)                       = 0
access("/nfs-home/.hushlogin", R_OK)    = -1 EACCES (Permission denied)
setuid(0)                               = 0
setreuid(0, 0)                          = 0
setregid(4294967295, 0)      


These system calls line up with the code from login.c:


  {
      char tmpstr[MAXPATHLEN];
      uid_t ruid = getuid();
      gid_t egid = getegid();

      /* avoid snprintf - old systems do not have it, or worse,
         have a libc in which snprintf is the same as sprintf */
      if (strlen(pwd->pw_dir) + sizeof(_PATH_HUSHLOGIN) + 2 > MAXPATHLEN)
              quietlog = 0;
      else {
              sprintf(tmpstr, "%s/%s", pwd->pw_dir, _PATH_HUSHLOGIN);
              setregid(-1, pwd->pw_gid);
              setreuid(0, pwd->pw_uid);
              quietlog = (access(tmpstr, R_OK) == 0);
              setuid(0); /* setreuid doesn't do it alone! */
              setreuid(ruid, 0);
              setregid(-1, egid);
      }


A small patch that uses setresuid and setresgid instead follows as attachement. It resolves the problem in my tests. I have not explored the consequences of using setresuid/setresgid fully, but I do think it is minimal.