SETFSUID (2)
set user identity used for file system checks
SYNOPSIS
int setfsuid(uid_t fsuid )
DESCRIPTION
setfsuid
sets the user ID that the Linux kernel uses to check for all accesses
to the file system. Normally, the value of
fsuid
will shadow the value of the effective user ID. In fact, whenever the
effective user ID is changed,
fsuid
will also be changed to new value of effective user ID.
An explict call to
setfsuid
is usually only used by programs such as the Linux NFS server that
need to change what user ID is used for file access without a
corresponding change in the real and effective user 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 from other user IDs.
setfsuid
will only succeed if the caller is the superuser or if
fsuid
matches either the real user ID, effective user ID, saved set-user-ID, or
the current value of
fsuid .
RETURN VALUE
On success, the previous value of
fsuid
is returned. On error, the current value of
fsuid
is returned.
CONFORMING TO
setfsuid
is Linux specific and should not be used in programs intended to be portable.
BUGS
No error messages of any kind are returned to the caller. At the very
least,
EPERM
should be returned when the call fails.
SEE ALSO
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