Langue: en

Version: 309570 (debian - 07/07/09)

Section: 9 (Appels noyau Linux)

BSD mandoc


suser suser_cred - check if credentials have superuser privileges


In sys/priv.h Ft int Fn suser struct thread *td Ft int Fn suser_cred struct ucred *cred int flag


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

The Fn 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 Fn 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 Fa flags field is currently unused.

The Fn suser and Fn 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.


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


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


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