Linux.com

setfsgid.2

SETFSGID

Section: Linux Programmer's Manual (2)
Updated: 2008-12-05
Index Return to Main Contents
 

NAME

setfsgid - set group identity used for file system checks  

SYNOPSIS

#include <unistd.h> /* glibc uses <sys/fsuid.h> */

int setfsgid(uid_t fsgid);  

DESCRIPTION

The system call setfsgid() sets the group ID that the Linux kernel uses to check for all accesses to the file system. Normally, the value of fsgid will shadow the value of the effective group ID. In fact, whenever the effective group ID is changed, fsgid will also be changed to the new value of the effective group ID.

Explicit calls to setfsuid(2) and setfsgid() are usually only used by programs such as the Linux NFS server that need to change what user and group ID is used for file access without a corresponding change in the real and effective user and group IDs. A change in the normal user IDs for a program such as the NFS server is a security hole that can expose it to unwanted signals. (But see below.)

setfsgid() will only succeed if the caller is the superuser or if fsgid matches either the real group ID, effective group ID, saved set-group-ID, or the current value of fsgid.  

RETURN VALUE

On success, the previous value of fsgid is returned. On error, the current value of fsgid is returned.  

VERSIONS

This system call is present in Linux since version 1.2.  

CONFORMING TO

setfsgid() is Linux-specific and should not be used in programs intended to be portable.  

NOTES

When glibc determines that the argument is not a valid group ID, it will return -1 and set errno to EINVAL without attempting the system call.

Note that at the time this system call was introduced, a process could send a signal to a process with the same effective user ID. Today signal permission handling is slightly different.  

BUGS

No error messages of any kind are returned to the caller. At the very least, EPERM should be returned when the call fails (because the caller lacks the CAP_SETGID capability).  

SEE ALSO

kill(2), setfsuid(2), capabilities(7), credentials(7)  

COLOPHON

This page is part of release 3.21 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
VERSIONS
CONFORMING TO
NOTES
BUGS
SEE ALSO
COLOPHON

 

Comments

Subscribe to Comments Feed

Upcoming Linux Foundation Courses

  1. LFD331 Developing Linux Device Drivers
    25 Aug » 29 Aug - Virtual
    Details
  2. LFS422 High Availability Linux Architecture
    08 Sep » 11 Sep - Raleigh, NC
    Details
  3. LFS426 Linux Performance Tuning
    08 Sep » 11 Sep - New York
    Details

View All Upcoming Courses

Become an Individual Member
Check out the Friday Funnies

Sign Up For the Linux.com Newsletter


Who we are ?

The Linux Foundation is a non-profit consortium dedicated to the growth of Linux.

More About the foundation...

Frequent Questions

Join / Linux Training / Board