4020272933
improve performance: - Eliminate custom reference count and condition variable to monitor threads entering the framework, as this had both significant overhead and behaved badly in the face of contention. - Replace reference count with two locks: an rwlock and an sx lock, which will be read-acquired by threads entering the framework depending on whether a give policy entry point is permitted to sleep or not. - Replace previous mutex locking of the reference count for exclusive access with write acquiring of both the policy list sx and rw locks, which occurs only when policies are attached or detached. - Do a lockless read of the dynamic policy list head before acquiring any locks in order to reduce overhead when no dynamic policies are loaded; this a race we can afford to lose. - For every policy entry point invocation, decide whether sleeping is permitted, and if not, use a _NOSLEEP() variant of the composition macros, which will use the rwlock instead of the sxlock. In some cases, we decide which to use based on allocation flags passed to the MAC Framework entry point. As with the move to rwlocks/rmlocks in pfil, this may trigger witness warnings, but these should (generally) be false positives as all acquisition of the locks is for read with two very narrow exceptions for policy load/unload, and those code blocks should never acquire other locks. Sponsored by: Google, Inc. Obtained from: TrustedBSD Project Discussed with: csjp (idea, not specific patch)
97 lines
3.2 KiB
C
97 lines
3.2 KiB
C
/*-
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* Copyright (c) 2006 nCircle Network Security, Inc.
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* Copyright (c) 2009 Robert N. M. Watson
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* All rights reserved.
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*
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* This software was developed by Robert N. M. Watson for the TrustedBSD
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* Project under contract to nCircle Network Security, Inc.
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*
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* This software was developed at the University of Cambridge Computer
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* Laboratory with support from a grant from Google, Inc.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR, NCIRCLE NETWORK SECURITY,
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* INC., OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
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* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* MAC checks for system privileges.
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*/
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#include "sys/cdefs.h"
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__FBSDID("$FreeBSD$");
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#include "opt_kdtrace.h"
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#include "opt_mac.h"
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#include <sys/param.h>
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#include <sys/kernel.h>
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#include <sys/priv.h>
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#include <sys/sdt.h>
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#include <sys/module.h>
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#include <security/mac/mac_framework.h>
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#include <security/mac/mac_internal.h>
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#include <security/mac/mac_policy.h>
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/*
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* The MAC Framework interacts with kernel privilege checks in two ways: it
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* may restrict the granting of privilege to a subject, and it may grant
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* additional privileges to the subject. Policies may implement none, one,
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* or both of these entry points. Restriction of privilege by any policy
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* always overrides granting of privilege by any policy or other privilege
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* mechanism. See kern_priv.c:priv_check_cred() for details of the
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* composition.
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*/
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MAC_CHECK_PROBE_DEFINE2(priv_check, "struct ucred *", "int");
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/*
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* Restrict access to a privilege for a credential. Return failure if any
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* policy denies access.
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*/
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int
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mac_priv_check(struct ucred *cred, int priv)
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{
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int error;
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MAC_CHECK_NOSLEEP(priv_check, cred, priv);
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MAC_CHECK_PROBE2(priv_check, error, cred, priv);
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return (error);
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}
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MAC_GRANT_PROBE_DEFINE2(priv_grant, "struct ucred *", "int");
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/*
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* Grant access to a privilege for a credential. Return success if any
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* policy grants access.
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*/
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int
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mac_priv_grant(struct ucred *cred, int priv)
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{
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int error;
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MAC_GRANT_NOSLEEP(priv_grant, cred, priv);
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MAC_GRANT_PROBE2(priv_grant, error, cred, priv);
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return (error);
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}
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