Bug 3568

Summary: RHSA: NFS root squashing broken with 32 bit uid_t
Product: [Retired] Red Hat Linux Reporter: Jeff Johnson <jbj>
Component: nfs-serverAssignee: Jay Turner <jturner>
Status: CLOSED CURRENTRELEASE QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: 5.2CC: srevivo
Target Milestone: ---   
Target Release: ---   
Hardware: All   
OS: Linux   
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Fixed In Version: Doc Type: Bug Fix
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Clone Of: Environment:
Last Closed: 1999-07-23 08:25:51 UTC Type: ---
Regression: --- Mount Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description Jeff Johnson 1999-06-18 12:01:03 UTC 
It's that time of the year again...
Someone just mailed me about a problem he was having with
unfsd, and
in passing he mentioned that Linux refuses setfsuid(-2).

Unfortunately, unfsd relies on this for root squashing
(unless you've
defined a different anon uid/gid).

The cause of the problem is glibc's move to 32 bit uid_t,
while the kernel remains at 16 bit.  To compensate for this,
the
glibc setfsuid() implementation has some hideously `clever'
code
(sysdeps/unix/sysv/linux/i386/setfsuid.c):

int
setfsuid (uid_t uid)
{
  if (uid != (uid_t) ((__kernel_uid_t) uid))
    {
      __set_errno (EINVAL);
      return -1;
    }

  return INLINE_SYSCALL (setfsuid, 1, uid);
}

It is entirely possible that other applications are affected
by these
symptoms as well, because seteuid exhibits the same
properties.

A patched unfsd (2.2.beta44) will be available shortly from
ftp://linux.mathematik.tu-darmstadt.de/pub/linux/people/okir
Comment 1 Jeff Johnson 1999-06-18 12:19:59 UTC 
Jay, this 5.2 errata package needs QA:
	5.2.2:	nfs-server-2.2beta44-1