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NAME | SYNOPSIS | DESCRIPTION | CALLBACKS | NETLINK NOTIFICATION | RETURN VALUE | NOTES | AUTHOR | SEE ALSO | COLOPHON |
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avc_init(3) SELinux API documentation avc_init(3)
avc_init - legacy userspace SELinux AVC setup
#include <selinux/selinux.h>
#include <selinux/avc.h>
int avc_init(const char *msgprefix,
const struct avc_memory_callback *mem_callbacks,
const struct avc_log_callback *log_callbacks,
const struct avc_thread_callback *thread_callbacks,
const struct avc_lock_callback *lock_callbacks);
avc_init() is deprecated; please use avc_open(3) in conjunction with
selinux_set_callback(3) in all new code.
avc_init() initializes the userspace AVC and must be called before
any other AVC operation can be performed. A non-NULL msgprefix will
be prepended to all audit messages produced by the userspace AVC.
The default is `uavc'. The remaining arguments, if non-NULL, specify
callbacks to be used by the userspace AVC.
The userspace AVC can be directed how to perform memory allocation,
logging, thread creation, and locking via callback functions passed
to avc_init(). The purpose of this functionality is to allow the
userspace AVC to be smoothly integrated into existing userspace
object managers.
Use an avc_memory_callback structure to specify alternate functions
for dynamic memory allocation.
struct avc_memory_callback {
void *(*func_malloc)(size_t size);
void (*func_free)(void *ptr);
};
The two fields of the structure should be pointers to functions which
behave as malloc(3) and free(3), which are used by default.
Use an avc_log_callback structure to specify alternate functions for
logging.
struct avc_log_callback {
void (*func_log)(const char *fmt, ...);
void (*func_audit)(void *auditdata,
security_class_t class,
char *msgbuf, size_t msgbufsize);
};
The func_log callback should accept a printf(3) style format and
arguments and log them as desired. The default behavior prints the
message on the standard error. The func_audit callback should
interpret the auditdata parameter for the given class, printing a
human-readable interpretation to msgbuf using no more than msgbufsize
characters. The default behavior is to ignore auditdata.
Use an avc_thread_callback structure to specify functions for
starting and manipulating threads.
struct avc_thread_callback {
void *(*func_create_thread)(void (*run)(void));
void (*func_stop_thread)(void *thread);
};
The func_create_thread callback should create a new thread and return
a pointer which references it. The thread should execute the run
argument, which does not return under normal conditions. The
func_stop_thread callback should cancel the running thread referenced
by thread. By default, threading is not used; see NETLINK
NOTIFICATION below.
Use an avc_lock_callback structure to specify functions to create,
obtain, and release locks for use by threads.
struct avc_lock_callback {
void *(*func_alloc_lock)(void);
void (*func_get_lock)(void *lock);
void (*func_release_lock)(void *lock);
void (*func_free_lock)(void *lock);
};
The func_alloc_lock callback should create a new lock, returning a
pointer which references it. The func_get_lock callback should
obtain lock, blocking if necessary. The func_release_lock callback
should release lock. The func_free_lock callback should destroy
lock, freeing any resources associated with it. The default behavior
is not to perform any locking. Note that undefined behavior may
result if threading is used without appropriate locking.
Beginning with version 2.6.4, the Linux kernel supports SELinux
status change notification via netlink. Two message types are
currently implemented, indicating changes to the enforcing mode and
to the loaded policy in the kernel, respectively. The userspace AVC
listens for these messages and takes the appropriate action,
modifying the behavior of avc_has_perm(3) to reflect the current
enforcing mode and flushing the cache on receipt of a policy load
notification. Audit messages are produced when netlink notifications
are processed.
In the default single-threaded mode, the userspace AVC checks for new
netlink messages at the start of each permission query. If threading
and locking callbacks are passed to avc_init() however, a dedicated
thread will be started to listen on the netlink socket. This may
increase performance and will ensure that log messages are generated
immediately rather than at the time of the next permission query.
Functions with a return value return zero on success. On error, -1
is returned and errno is set appropriately.
The msgprefix argument to avc_init() currently has a length limit of
15 characters and will be truncated if necessary.
If a provided func_malloc callback does not set errno appropriately
on error, userspace AVC calls may exhibit the same behavior.
If a netlink thread has been created and an error occurs on the
socket (such as an access error), the thread may terminate and cause
the userspace AVC to return EINVAL on all further permission checks
until avc_destroy is called.
Eamon Walsh <ewalsh@tycho.nsa.gov>
avc_open(3), selinux_set_callback(3), selinux(8)
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 2018-02-02. (At that
time, the date of the most recent commit that was found in the repos‐
itory was 2018-01-25.) 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
27 May 2004 avc_init(3)
Pages that refer to this page: avc_add_callback(3), avc_cache_stats(3), avc_compute_create(3), avc_context_to_sid(3), avc_has_perm(3), selinux_set_callback(3)
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