selinux_status_open(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | SEE ALSO | COLOPHON

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_status_deny_unknown -
       reference the SELinux kernel status without invocation 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
       monitoring.

       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 error.

       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 reloaded.

       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),
       security_deny_unknown(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 
       ⟨https://github.com/SELinuxProject/selinux/wiki⟩.  If you have a
       bug report for this manual page, see
       ⟨https://github.com/SELinuxProject/selinux/wiki/Contributing⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/SELinuxProject/selinux⟩ on 2021-04-01.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2021-03-18.)  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 improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

kaigai@ak.jp.nec.com         22 January 2011      selinux_status_open(3)

Pages that refer to this page: avc_init(3)avc_open(3)