selinux_status_deny_unknown(3) — Linux manual page


selinux_status_open(3)    SELinux API documentation   selinux_status_open(3)

NAME         top

       selinux_status_open,   selinux_status_close,  selinux_status_updated,
       selinux_status_getenforce, selinux_status_policyload and selinux_sta‐
       tus_deny_unknown  - reference the SELinux kernel status without invo‐
       cation of system calls

SYNOPSIS         top

       #include <selinux/avc.h>

       int selinux_status_open(int fallback);

       void selinux_status_close(void);

       int selinux_status_updated(void);

       int selinux_status_getenforce(void);

       int selinux_status_policyload(void);

       int selinux_status_deny_unknown(void);

DESCRIPTION         top

       Linux 2.6.37 or later provides a SELinux kernel status page; being
       mostly placed on /sys/fs/selinux/status entry. It enables userspace
       applications to mmap this page with read-only mode, then it informs
       some status without system call invocations.

       In some cases that a userspace application tries to apply heavy
       frequent access control; such as row-level security in databases, it
       will face unignorable cost to communicate with kernel space to check
       invalidation of userspace avc.

       These functions provides applications a way to know some kernel
       events without system-call invocation or worker thread for

       selinux_status_open() tries to open(2) /sys/fs/selinux/status and
       mmap(2) it in read-only mode. The file-descriptor and pointer to the
       page shall be stored internally; Don't touch them directly.  Set 1 on
       the fallback argument to handle a case of older kernels without
       kernel status page support.  In this case, this function tries to
       open a netlink socket using avc_netlink_open(3) and overwrite
       corresponding callbacks (setenforce and policyload).  Thus, we need
       to pay attention to the interaction with these interfaces, when
       fallback mode is enabled.

       selinux_status_close() unmap the kernel status page and close its
       file descriptor, or close the netlink socket if fallbacked.

       selinux_status_updated() processes status update events. There are
       two kinds of status updates.  setenforce events will change the
       effective enforcing state used within the AVC, and policyload events
       will result in a cache flush.

       This function returns 0 if there have been no updates since the last
       call, 1 if there have been updates since the last call, or -1 on

       selinux_status_getenforce() returns 0 if SELinux is running in
       permissive mode, 1 if enforcing mode, or -1 on error.  Same as
       security_getenforce(3) except with or without system call invocation.

       selinux_status_policyload() returns times of policy reloaded on the
       running system, or -1 on error.  Note that it is not a reliable value
       on fallback-mode until it receive the first event message via netlink
       socket.  Thus, don't use this value to know actual times of policy

       selinux_status_deny_unknown() returns 0 if SELinux treats policy
       queries on undefined object classes or permissions as being allowed,
       1 if such queries are denied, or -1 on error.

       Also note that these interfaces are not thread-safe, so you have to
       protect them from concurrent calls using exclusive locks when
       multiple threads are performing.

RETURN VALUE         top

       selinux_status_open() returns 0 or 1 on success. 1 means we are ready
       to use these interfaces, but netlink socket was opened as fallback
       instead of the kernel status page.  On error, -1 shall be returned.

       Any other functions with a return value shall return its
       characteristic value as described above, or -1 on errors.

SEE ALSO         top

       mmap(2), avc_netlink_open(3), security_getenforce(3),

COLOPHON         top

       This page is part of the selinux (Security-Enhanced Linux user-space
       libraries and tools) project.  Information about the project can be
       found at ⟨⟩.  If you
       have a bug report for this manual page, see
       ⟨⟩.  This
       page was obtained from the project's upstream Git repository
       ⟨⟩ on 2020-11-01.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-10-31.)  If you discover any rendering problems in
       this HTML version of the page, or you believe there is a better or
       more up-to-date source for the page, or you have corrections or im‐
       provements to the information in this COLOPHON (which is not part of
       the original manual page), send a mail to           22 January 2011        selinux_status_open(3)