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.\" Copyright (C) 1997 Andries Brouwer (aeb@cwi.nl)
.\"
+.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
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.\" Modified, 2003-05-26, Michael Kerrisk, <mtk.manpages@gmail.com>
-.TH SETRESUID 2 2010-11-22 "Linux" "Linux Programmer's Manual"
+.TH SETRESUID 2 2014-09-21 "Linux" "Linux Programmer's Manual"
.SH NAME
setresuid, setresgid \- set real, effective and saved user or group ID
.SH SYNOPSIS
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 file system UID is always set to the same
+and saved set-user-ID, the filesystem UID is always set to the same
value as the (possibly new) effective UID.
Completely analogously,
.BR setresgid ()
sets the real GID, effective GID, and saved set-group-ID
-of the calling process (and always modifies the file system GID
+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.
-.SH "RETURN VALUE"
+.SH RETURN VALUE
On success, zero is returned.
On error, \-1 is returned, and
.I errno
is set appropriately.
+
+.IR Note :
+there are cases where
+.BR setresuid ()
+can fail even when the caller is UID 0;
+it is a grave security error to omit checking for a failure return from
+.BR setresuid ().
.SH ERRORS
.TP
.B EAGAIN
-.I uid
-does not match the current UID and this call would
-bring that user ID over its
+The call would change the caller's real UID (i.e.,
+.I ruid
+does not match the caller's real UID),
+but there was a temporary failure allocating the
+necessary kernel data structures.
+.TP
+.B EAGAIN
+.I ruid
+does not match the caller's real UID and this call would
+bring the number of processes belonging to the real user ID
+.I ruid
+over the caller's
.B 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
+.B EAGAIN
+in
+.BR execve (2).
+.TP
+.B EINVAL
+One or more of the target user or group IDs
+is not valid in this user namespace.
.TP
.B EPERM
The calling process is not privileged (did not have the \fBCAP_SETUID\fP
capability) and tried to change the IDs to values that are not permitted.
.SH VERSIONS
These calls are available under Linux since Linux 2.1.44.
-.SH "CONFORMING TO"
+.SH CONFORMING TO
These calls are nonstandard;
they also appear on HP-UX and some of the BSDs.
.SH NOTES
Under HP-UX and FreeBSD, the prototype is found in
.IR <unistd.h> .
-Under Linux the prototype is provided by glibc since version 2.3.2.
+Under Linux, the prototype is provided by glibc since version 2.3.2.
The original Linux
.BR setresuid ()
and
.BR setresgid ()
wrapper functions transparently deal with the variations across kernel versions.
-.SH "SEE ALSO"
+.SH SEE ALSO
.BR getresuid (2),
.BR getuid (2),
.BR setfsgid (2),
.BR setreuid (2),
.BR setuid (2),
.BR capabilities (7),
-.BR credentials (7)
+.BR credentials (7),
+.BR user_namespaces (7)
+.SH COLOPHON
+This page is part of release 3.79 of the Linux
+.I 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/.
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