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SETRESUID(2) Linux Programmer's Manual SETRESUID(2)
NAME
setresuid, setresgid - set real, effective and saved user or group ID
SYNOPSIS
#define _GNU_SOURCE /* See feature_test_macros(7) */
#include <unistd.h>
int setresuid(uid_t ruid, uid_t euid, uid_t suid);
int setresgid(gid_t rgid, gid_t egid, gid_t sgid);
DESCRIPTION
setresuid() sets the real user ID, the effective user ID, and the saved
set-user-ID of the calling process.
Unprivileged user processes may change the real UID, effective UID, and
saved set-user-ID, each to one of: the current real UID, the current
effective UID or the current saved set-user-ID.
Privileged processes (on Linux, those having the CAP_SETUID capability)
may set the real UID, effective UID, and saved set-user-ID to arbitrary
values.
If one of the arguments equals -1, the corresponding value is not
changed.
Regardless of what changes are made to the real UID, effective UID, and
saved set-user-ID, the filesystem UID is always set to the same value
as the (possibly new) effective UID.
Completely analogously, setresgid() sets the real GID, effective GID,
and saved set-group-ID of the calling process (and always modifies the
filesystem GID to be the same as the effective GID), with the same
restrictions for unprivileged processes.
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is
set appropriately.
Note: there are cases where setresuid() can fail even when the caller
is UID 0; it is a grave security error to omit checking for a failure
return from setresuid().
ERRORS
EAGAIN The call would change the caller's real UID (i.e., ruid does not
match the caller's real UID), but there was a temporary failure
allocating the necessary kernel data structures.
EAGAIN ruid does not match the caller's real UID and this call would
bring the number of processes belonging to the real user ID ruid
over the caller's RLIMIT_NPROC resource limit. Since Linux 3.1,
this error case no longer occurs (but robust applications should
check for this error); see the description of EAGAIN in
execve(2).
EPERM The calling process is not privileged (did not have the
CAP_SETUID capability) and tried to change the IDs to values
that are not permitted.
VERSIONS
These calls are available under Linux since Linux 2.1.44.
CONFORMING TO
These calls are nonstandard; they also appear on HP-UX and some of the
BSDs.
NOTES
Under HP-UX and FreeBSD, the prototype is found in <unistd.h>. Under
Linux the prototype is provided by glibc since version 2.3.2.
The original Linux setresuid() and setresgid() system calls supported
only 16-bit user and group IDs. Subsequently, Linux 2.4 added setre-
suid32() and setresgid32(), supporting 32-bit IDs. The glibc setre-
suid() and setresgid() wrapper functions transparently deal with the
variations across kernel versions.
SEE ALSO
getresuid(2), getuid(2), setfsgid(2), setfsuid(2), setreuid(2),
setuid(2), capabilities(7), credentials(7)
COLOPHON
This page is part of release 3.69 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
http://www.kernel.org/doc/man-pages/.
Linux 2014-06-13 SETRESUID(2)
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