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NAME
     suser, suser_cred - check if credentials have superuser privileges


SYNOPSIS
     #include <sys/priv.h>

     int
     suser(struct thread *td);

     int
     suser_cred(struct ucred *cred, int flag);


DESCRIPTION
     The suser() and suser_cred() functions check if the credentials given
     include superuser powers.

     These interfaces have now been obsoleted by priv(9), and are provided
     only for compatibility with third party kernel modules that have not yet
     been updated to the new interface.  They should not be used in any new
     kernel code.

     The suser() function is the most common, and should be used unless
     special circumstances dictate otherwise.

     The suser_cred() function should be used when the credentials to be
     checked are not the thread’s own, when there is no thread, when superuser
     powers should be extended to imprisoned roots, or when the credential to
     be checked is the real user rather than the effective user.

     Whether or not a privilege is permitted in a jail(8) depends on logic in
     prison_priv_check().

     In general, privileges are assigned based on the effective user ID; in
     some cases, the real user ID may be used.

     The flags field is currently unused.

     The suser() and suser_cred() functions note the fact that superuser
     powers have been used in the process structure of the process specified.
     Because part of their function is to notice whether superuser powers have
     been used, the functions should only be called after other permission
     possibilities have been exhausted.


RETURN VALUES
     The suser() and suser_cred() functions return 0 if the user has superuser
     powers and EPERM otherwise.  This is the reverse logic of some other
     implementations of suser() in which a TRUE response indicates superuser
     powers.


SEE ALSO
     chroot(2), jail(2), priv(9)


BUGS
     The suser() and suser_cred() functions do not, in fact, record that
     superuser privileges have been used, and have not done so since August
     2000.