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Expand commenting on label slots, justification for the MAC Framework locking

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model, interactions between locking and policy init/destroy methods.

Rewrap some comments to 77 character line wrap.

Obtained from:	TrustedBSD Project
This commit is contained in:
rwatson 2006-12-20 20:38:44 +00:00
parent da8c5f8136
commit 5749ecccba
3 changed files with 237 additions and 162 deletions
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133
sys/kern/kern_mac.c
View File

@ -106,6 +106,16 @@ MODULE_VERSION(kernel_mac_support, 3);
SYSCTL_NODE(_security, OID_AUTO, mac, CTLFLAG_RW, 0,
"TrustedBSD MAC policy controls");
/*
* Labels consist of a indexed set of "slots", which are allocated policies
* as required. The MAC Framework maintains a bitmask of slots allocated so
* far to prevent reuse. Slots cannot be reused, as the MAC Framework
* guarantees that newly allocated slots in labels will be NULL unless
* otherwise initialized, and because we do not have a mechanism to garbage
* collect slots on policy unload. As labeled policies tend to be statically
* loaded during boot, and not frequently unloaded and reloaded, this is not
* generally an issue.
*/
#if MAC_MAX_SLOTS > 32
#error "MAC_MAX_SLOTS too large"
#endif
@ -123,15 +133,18 @@ SYSCTL_UINT(_security_mac, OID_AUTO, max_slots, CTLFLAG_RD,
int mac_late = 0;
/*
* Flag to indicate whether or not we should allocate label storage for
* new mbufs. Since most dynamic policies we currently work with don't
* rely on mbuf labeling, try to avoid paying the cost of mtag allocation
* unless specifically notified of interest. One result of this is
* that if a dynamically loaded policy requests mbuf labels, it must
* be able to deal with a NULL label being returned on any mbufs that
* were already in flight when the policy was loaded. Since the policy
* already has to deal with uninitialized labels, this probably won't
* be a problem. Note: currently no locking. Will this be a problem?
* Flag to indicate whether or not we should allocate label storage for new
* mbufs. Since most dynamic policies we currently work with don't rely on
* mbuf labeling, try to avoid paying the cost of mtag allocation unless
* specifically notified of interest. One result of this is that if a
* dynamically loaded policy requests mbuf labels, it must be able to deal
* with a NULL label being returned on any mbufs that were already in flight
* when the policy was loaded. Since the policy already has to deal with
* uninitialized labels, this probably won't be a problem. Note: currently
* no locking. Will this be a problem?
*
* In the future, we may want to allow objects to request labeling on a per-
* object type basis, rather than globally for all objects.
*/
#ifndef MAC_ALWAYS_LABEL_MBUF
int mac_labelmbufs = 0;
@ -143,22 +156,31 @@ static int mac_policy_unregister(struct mac_policy_conf *mpc);
MALLOC_DEFINE(M_MACTEMP, "mactemp", "MAC temporary label storage");
/*
* mac_static_policy_list holds a list of policy modules that are not
* loaded while the system is "live", and cannot be unloaded. These
* policies can be invoked without holding the busy count.
* mac_static_policy_list holds a list of policy modules that are not loaded
* while the system is "live", and cannot be unloaded. These policies can be
* invoked without holding the busy count.
*
* mac_policy_list stores the list of dynamic policies. A busy count is
* maintained for the list, stored in mac_policy_busy. The busy count
* is protected by mac_policy_mtx; the list may be modified only
* while the busy count is 0, requiring that the lock be held to
* prevent new references to the list from being acquired. For almost
* all operations, incrementing the busy count is sufficient to
* guarantee consistency, as the list cannot be modified while the
* busy count is elevated. For a few special operations involving a
* change to the list of active policies, the mtx itself must be held.
* A condition variable, mac_policy_cv, is used to signal potential
* exclusive consumers that they should try to acquire the lock if a
* first attempt at exclusive access fails.
* maintained for the list, stored in mac_policy_busy. The busy count is
* protected by mac_policy_mtx; the list may be modified only while the busy
* count is 0, requiring that the lock be held to prevent new references to
* the list from being acquired. For almost all operations, incrementing the
* busy count is sufficient to guarantee consistency, as the list cannot be
* modified while the busy count is elevated. For a few special operations
* involving a change to the list of active policies, the mtx itself must be
* held. A condition variable, mac_policy_cv, is used to signal potential
* exclusive consumers that they should try to acquire the lock if a first
* attempt at exclusive access fails.
*
* This design intentionally avoids fairness, and may starve attempts to
* acquire an exclusive lock on a busy system. This is required because we
* do not ever want acquiring a read reference to perform an unbounded length
* sleep. Read references are acquired in ithreads, network isrs, etc, and
* any unbounded blocking could lead quickly to deadlock.
*
* Another reason for never blocking on read references is that the MAC
* Framework may recurse: if a policy calls a VOP, for example, this might
* lead to vnode life cycle operations (such as init/destroy).
*/
#ifndef MAC_STATIC
static struct mtx mac_policy_mtx;
@ -169,13 +191,12 @@ struct mac_policy_list_head mac_policy_list;
struct mac_policy_list_head mac_static_policy_list;
/*
* We manually invoke WITNESS_WARN() to allow Witness to generate
* warnings even if we don't end up ever triggering the wait at
* run-time. The consumer of the exclusive interface must not hold
* any locks (other than potentially Giant) since we may sleep for
* long (potentially indefinite) periods of time waiting for the
* framework to become quiescent so that a policy list change may
* be made.
* We manually invoke WITNESS_WARN() to allow Witness to generate warnings
* even if we don't end up ever triggering the wait at run-time. The
* consumer of the exclusive interface must not hold any locks (other than
* potentially Giant) since we may sleep for long (potentially indefinite)
* periods of time waiting for the framework to become quiescent so that a
* policy list change may be made.
*/
void
mac_policy_grab_exclusive(void)
@ -296,9 +317,9 @@ mac_init(void)
}
/*
* For the purposes of modules that want to know if they were loaded
* "early", set the mac_late flag once we've processed modules either
* linked into the kernel, or loaded before the kernel startup.
* For the purposes of modules that want to know if they were loaded "early",
* set the mac_late flag once we've processed modules either linked into the
* kernel, or loaded before the kernel startup.
*/
static void
mac_late_init(void)
@ -310,8 +331,8 @@ mac_late_init(void)
/*
* After the policy list has changed, walk the list to update any global
* flags. Currently, we support only one flag, and it's conditionally
* defined; as a result, the entire function is conditional. Eventually,
* the #else case might also iterate across the policies.
* defined; as a result, the entire function is conditional. Eventually, the
* #else case might also iterate across the policies.
*/
static void
mac_policy_updateflags(void)
@ -390,16 +411,16 @@ mac_policy_register(struct mac_policy_conf *mpc)
error = 0;
/*
* We don't technically need exclusive access while !mac_late,
* but hold it for assertion consistency.
* We don't technically need exclusive access while !mac_late, but
* hold it for assertion consistency.
*/
mac_policy_grab_exclusive();
/*
* If the module can potentially be unloaded, or we're loading
* late, we have to stick it in the non-static list and pay
* an extra performance overhead. Otherwise, we can pay a
* light locking cost and stick it in the static list.
* If the module can potentially be unloaded, or we're loading late,
* we have to stick it in the non-static list and pay an extra
* performance overhead. Otherwise, we can pay a light locking cost
* and stick it in the static list.
*/
static_entry = (!mac_late &&
!(mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK));
@ -432,18 +453,23 @@ mac_policy_register(struct mac_policy_conf *mpc)
mpc->mpc_runtime_flags |= MPC_RUNTIME_FLAG_REGISTERED;
/*
* If we're loading a MAC module after the framework has
* initialized, it has to go into the dynamic list. If
* we're loading it before we've finished initializing,
* it can go into the static list with weaker locker
* requirements.
* If we're loading a MAC module after the framework has initialized,
* it has to go into the dynamic list. If we're loading it before
* we've finished initializing, it can go into the static list with
* weaker locker requirements.
*/
if (static_entry)
LIST_INSERT_HEAD(&mac_static_policy_list, mpc, mpc_list);
else
LIST_INSERT_HEAD(&mac_policy_list, mpc, mpc_list);
/* Per-policy initialization. */
/*
* Per-policy initialization. Currently, this takes place under the
* exclusive lock, so policies must not sleep in their init method.
* In the future, we may want to separate "init" from "start", with
* "init" occuring without the lock held. Likewise, on tear-down,
* breaking out "stop" from "destroy".
*/
if (mpc->mpc_ops->mpo_init != NULL)
(*(mpc->mpc_ops->mpo_init))(mpc);
mac_policy_updateflags();
@ -461,9 +487,8 @@ mac_policy_unregister(struct mac_policy_conf *mpc)
{
/*
* If we fail the load, we may get a request to unload. Check
* to see if we did the run-time registration, and if not,
* silently succeed.
* If we fail the load, we may get a request to unload. Check to see
* if we did the run-time registration, and if not, silently succeed.
*/
mac_policy_grab_exclusive();
if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED) == 0) {
@ -480,8 +505,8 @@ mac_policy_unregister(struct mac_policy_conf *mpc)
}
#endif
/*
* Only allow the unload to proceed if the module is unloadable
* by its own definition.
* Only allow the unload to proceed if the module is unloadable by
* its own definition.
*/
if ((mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK) == 0) {
mac_policy_release_exclusive();
@ -710,8 +735,8 @@ __mac_set_proc(struct thread *td, struct __mac_set_proc_args *uap)
p->p_ucred = newcred;
/*
* Grab additional reference for use while revoking mmaps, prior
* to releasing the proc lock and sharing the cred.
* Grab additional reference for use while revoking mmaps, prior to
* releasing the proc lock and sharing the cred.
*/
crhold(newcred);
PROC_UNLOCK(p);

133
sys/security/mac/mac_framework.c
View File

@ -106,6 +106,16 @@ MODULE_VERSION(kernel_mac_support, 3);
SYSCTL_NODE(_security, OID_AUTO, mac, CTLFLAG_RW, 0,
"TrustedBSD MAC policy controls");
/*
* Labels consist of a indexed set of "slots", which are allocated policies
* as required. The MAC Framework maintains a bitmask of slots allocated so
* far to prevent reuse. Slots cannot be reused, as the MAC Framework
* guarantees that newly allocated slots in labels will be NULL unless
* otherwise initialized, and because we do not have a mechanism to garbage
* collect slots on policy unload. As labeled policies tend to be statically
* loaded during boot, and not frequently unloaded and reloaded, this is not
* generally an issue.
*/
#if MAC_MAX_SLOTS > 32
#error "MAC_MAX_SLOTS too large"
#endif
@ -123,15 +133,18 @@ SYSCTL_UINT(_security_mac, OID_AUTO, max_slots, CTLFLAG_RD,
int mac_late = 0;
/*
* Flag to indicate whether or not we should allocate label storage for
* new mbufs. Since most dynamic policies we currently work with don't
* rely on mbuf labeling, try to avoid paying the cost of mtag allocation
* unless specifically notified of interest. One result of this is
* that if a dynamically loaded policy requests mbuf labels, it must
* be able to deal with a NULL label being returned on any mbufs that
* were already in flight when the policy was loaded. Since the policy
* already has to deal with uninitialized labels, this probably won't
* be a problem. Note: currently no locking. Will this be a problem?
* Flag to indicate whether or not we should allocate label storage for new
* mbufs. Since most dynamic policies we currently work with don't rely on
* mbuf labeling, try to avoid paying the cost of mtag allocation unless
* specifically notified of interest. One result of this is that if a
* dynamically loaded policy requests mbuf labels, it must be able to deal
* with a NULL label being returned on any mbufs that were already in flight
* when the policy was loaded. Since the policy already has to deal with
* uninitialized labels, this probably won't be a problem. Note: currently
* no locking. Will this be a problem?
*
* In the future, we may want to allow objects to request labeling on a per-
* object type basis, rather than globally for all objects.
*/
#ifndef MAC_ALWAYS_LABEL_MBUF
int mac_labelmbufs = 0;
@ -143,22 +156,31 @@ static int mac_policy_unregister(struct mac_policy_conf *mpc);
MALLOC_DEFINE(M_MACTEMP, "mactemp", "MAC temporary label storage");
/*
* mac_static_policy_list holds a list of policy modules that are not
* loaded while the system is "live", and cannot be unloaded. These
* policies can be invoked without holding the busy count.
* mac_static_policy_list holds a list of policy modules that are not loaded
* while the system is "live", and cannot be unloaded. These policies can be
* invoked without holding the busy count.
*
* mac_policy_list stores the list of dynamic policies. A busy count is
* maintained for the list, stored in mac_policy_busy. The busy count
* is protected by mac_policy_mtx; the list may be modified only
* while the busy count is 0, requiring that the lock be held to
* prevent new references to the list from being acquired. For almost
* all operations, incrementing the busy count is sufficient to
* guarantee consistency, as the list cannot be modified while the
* busy count is elevated. For a few special operations involving a
* change to the list of active policies, the mtx itself must be held.
* A condition variable, mac_policy_cv, is used to signal potential
* exclusive consumers that they should try to acquire the lock if a
* first attempt at exclusive access fails.
* maintained for the list, stored in mac_policy_busy. The busy count is
* protected by mac_policy_mtx; the list may be modified only while the busy
* count is 0, requiring that the lock be held to prevent new references to
* the list from being acquired. For almost all operations, incrementing the
* busy count is sufficient to guarantee consistency, as the list cannot be
* modified while the busy count is elevated. For a few special operations
* involving a change to the list of active policies, the mtx itself must be
* held. A condition variable, mac_policy_cv, is used to signal potential
* exclusive consumers that they should try to acquire the lock if a first
* attempt at exclusive access fails.
*
* This design intentionally avoids fairness, and may starve attempts to
* acquire an exclusive lock on a busy system. This is required because we
* do not ever want acquiring a read reference to perform an unbounded length
* sleep. Read references are acquired in ithreads, network isrs, etc, and
* any unbounded blocking could lead quickly to deadlock.
*
* Another reason for never blocking on read references is that the MAC
* Framework may recurse: if a policy calls a VOP, for example, this might
* lead to vnode life cycle operations (such as init/destroy).
*/
#ifndef MAC_STATIC
static struct mtx mac_policy_mtx;
@ -169,13 +191,12 @@ struct mac_policy_list_head mac_policy_list;
struct mac_policy_list_head mac_static_policy_list;
/*
* We manually invoke WITNESS_WARN() to allow Witness to generate
* warnings even if we don't end up ever triggering the wait at
* run-time. The consumer of the exclusive interface must not hold
* any locks (other than potentially Giant) since we may sleep for
* long (potentially indefinite) periods of time waiting for the
* framework to become quiescent so that a policy list change may
* be made.
* We manually invoke WITNESS_WARN() to allow Witness to generate warnings
* even if we don't end up ever triggering the wait at run-time. The
* consumer of the exclusive interface must not hold any locks (other than
* potentially Giant) since we may sleep for long (potentially indefinite)
* periods of time waiting for the framework to become quiescent so that a
* policy list change may be made.
*/
void
mac_policy_grab_exclusive(void)
@ -296,9 +317,9 @@ mac_init(void)
}
/*
* For the purposes of modules that want to know if they were loaded
* "early", set the mac_late flag once we've processed modules either
* linked into the kernel, or loaded before the kernel startup.
* For the purposes of modules that want to know if they were loaded "early",
* set the mac_late flag once we've processed modules either linked into the
* kernel, or loaded before the kernel startup.
*/
static void
mac_late_init(void)
@ -310,8 +331,8 @@ mac_late_init(void)
/*
* After the policy list has changed, walk the list to update any global
* flags. Currently, we support only one flag, and it's conditionally
* defined; as a result, the entire function is conditional. Eventually,
* the #else case might also iterate across the policies.
* defined; as a result, the entire function is conditional. Eventually, the
* #else case might also iterate across the policies.
*/
static void
mac_policy_updateflags(void)
@ -390,16 +411,16 @@ mac_policy_register(struct mac_policy_conf *mpc)
error = 0;
/*
* We don't technically need exclusive access while !mac_late,
* but hold it for assertion consistency.
* We don't technically need exclusive access while !mac_late, but
* hold it for assertion consistency.
*/
mac_policy_grab_exclusive();
/*
* If the module can potentially be unloaded, or we're loading
* late, we have to stick it in the non-static list and pay
* an extra performance overhead. Otherwise, we can pay a
* light locking cost and stick it in the static list.
* If the module can potentially be unloaded, or we're loading late,
* we have to stick it in the non-static list and pay an extra
* performance overhead. Otherwise, we can pay a light locking cost
* and stick it in the static list.
*/
static_entry = (!mac_late &&
!(mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK));
@ -432,18 +453,23 @@ mac_policy_register(struct mac_policy_conf *mpc)
mpc->mpc_runtime_flags |= MPC_RUNTIME_FLAG_REGISTERED;
/*
* If we're loading a MAC module after the framework has
* initialized, it has to go into the dynamic list. If
* we're loading it before we've finished initializing,
* it can go into the static list with weaker locker
* requirements.
* If we're loading a MAC module after the framework has initialized,
* it has to go into the dynamic list. If we're loading it before
* we've finished initializing, it can go into the static list with
* weaker locker requirements.
*/
if (static_entry)
LIST_INSERT_HEAD(&mac_static_policy_list, mpc, mpc_list);
else
LIST_INSERT_HEAD(&mac_policy_list, mpc, mpc_list);
/* Per-policy initialization. */
/*
* Per-policy initialization. Currently, this takes place under the
* exclusive lock, so policies must not sleep in their init method.
* In the future, we may want to separate "init" from "start", with
* "init" occuring without the lock held. Likewise, on tear-down,
* breaking out "stop" from "destroy".
*/
if (mpc->mpc_ops->mpo_init != NULL)
(*(mpc->mpc_ops->mpo_init))(mpc);
mac_policy_updateflags();
@ -461,9 +487,8 @@ mac_policy_unregister(struct mac_policy_conf *mpc)
{
/*
* If we fail the load, we may get a request to unload. Check
* to see if we did the run-time registration, and if not,
* silently succeed.
* If we fail the load, we may get a request to unload. Check to see
* if we did the run-time registration, and if not, silently succeed.
*/
mac_policy_grab_exclusive();
if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED) == 0) {
@ -480,8 +505,8 @@ mac_policy_unregister(struct mac_policy_conf *mpc)
}
#endif
/*
* Only allow the unload to proceed if the module is unloadable
* by its own definition.
* Only allow the unload to proceed if the module is unloadable by
* its own definition.
*/
if ((mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK) == 0) {
mac_policy_release_exclusive();
@ -710,8 +735,8 @@ __mac_set_proc(struct thread *td, struct __mac_set_proc_args *uap)
p->p_ucred = newcred;
/*
* Grab additional reference for use while revoking mmaps, prior
* to releasing the proc lock and sharing the cred.
* Grab additional reference for use while revoking mmaps, prior to
* releasing the proc lock and sharing the cred.
*/
crhold(newcred);
PROC_UNLOCK(p);

133
sys/security/mac/mac_syscalls.c
View File

@ -106,6 +106,16 @@ MODULE_VERSION(kernel_mac_support, 3);
SYSCTL_NODE(_security, OID_AUTO, mac, CTLFLAG_RW, 0,
"TrustedBSD MAC policy controls");
/*
* Labels consist of a indexed set of "slots", which are allocated policies
* as required. The MAC Framework maintains a bitmask of slots allocated so
* far to prevent reuse. Slots cannot be reused, as the MAC Framework
* guarantees that newly allocated slots in labels will be NULL unless
* otherwise initialized, and because we do not have a mechanism to garbage
* collect slots on policy unload. As labeled policies tend to be statically
* loaded during boot, and not frequently unloaded and reloaded, this is not
* generally an issue.
*/
#if MAC_MAX_SLOTS > 32
#error "MAC_MAX_SLOTS too large"
#endif
@ -123,15 +133,18 @@ SYSCTL_UINT(_security_mac, OID_AUTO, max_slots, CTLFLAG_RD,
int mac_late = 0;
/*
* Flag to indicate whether or not we should allocate label storage for
* new mbufs. Since most dynamic policies we currently work with don't
* rely on mbuf labeling, try to avoid paying the cost of mtag allocation
* unless specifically notified of interest. One result of this is
* that if a dynamically loaded policy requests mbuf labels, it must
* be able to deal with a NULL label being returned on any mbufs that
* were already in flight when the policy was loaded. Since the policy
* already has to deal with uninitialized labels, this probably won't
* be a problem. Note: currently no locking. Will this be a problem?
* Flag to indicate whether or not we should allocate label storage for new
* mbufs. Since most dynamic policies we currently work with don't rely on
* mbuf labeling, try to avoid paying the cost of mtag allocation unless
* specifically notified of interest. One result of this is that if a
* dynamically loaded policy requests mbuf labels, it must be able to deal
* with a NULL label being returned on any mbufs that were already in flight
* when the policy was loaded. Since the policy already has to deal with
* uninitialized labels, this probably won't be a problem. Note: currently
* no locking. Will this be a problem?
*
* In the future, we may want to allow objects to request labeling on a per-
* object type basis, rather than globally for all objects.
*/
#ifndef MAC_ALWAYS_LABEL_MBUF
int mac_labelmbufs = 0;
@ -143,22 +156,31 @@ static int mac_policy_unregister(struct mac_policy_conf *mpc);
MALLOC_DEFINE(M_MACTEMP, "mactemp", "MAC temporary label storage");
/*
* mac_static_policy_list holds a list of policy modules that are not
* loaded while the system is "live", and cannot be unloaded. These
* policies can be invoked without holding the busy count.
* mac_static_policy_list holds a list of policy modules that are not loaded
* while the system is "live", and cannot be unloaded. These policies can be
* invoked without holding the busy count.
*
* mac_policy_list stores the list of dynamic policies. A busy count is
* maintained for the list, stored in mac_policy_busy. The busy count
* is protected by mac_policy_mtx; the list may be modified only
* while the busy count is 0, requiring that the lock be held to
* prevent new references to the list from being acquired. For almost
* all operations, incrementing the busy count is sufficient to
* guarantee consistency, as the list cannot be modified while the
* busy count is elevated. For a few special operations involving a
* change to the list of active policies, the mtx itself must be held.
* A condition variable, mac_policy_cv, is used to signal potential
* exclusive consumers that they should try to acquire the lock if a
* first attempt at exclusive access fails.
* maintained for the list, stored in mac_policy_busy. The busy count is
* protected by mac_policy_mtx; the list may be modified only while the busy
* count is 0, requiring that the lock be held to prevent new references to
* the list from being acquired. For almost all operations, incrementing the
* busy count is sufficient to guarantee consistency, as the list cannot be
* modified while the busy count is elevated. For a few special operations
* involving a change to the list of active policies, the mtx itself must be
* held. A condition variable, mac_policy_cv, is used to signal potential
* exclusive consumers that they should try to acquire the lock if a first
* attempt at exclusive access fails.
*
* This design intentionally avoids fairness, and may starve attempts to
* acquire an exclusive lock on a busy system. This is required because we
* do not ever want acquiring a read reference to perform an unbounded length
* sleep. Read references are acquired in ithreads, network isrs, etc, and
* any unbounded blocking could lead quickly to deadlock.
*
* Another reason for never blocking on read references is that the MAC
* Framework may recurse: if a policy calls a VOP, for example, this might
* lead to vnode life cycle operations (such as init/destroy).
*/
#ifndef MAC_STATIC
static struct mtx mac_policy_mtx;
@ -169,13 +191,12 @@ struct mac_policy_list_head mac_policy_list;
struct mac_policy_list_head mac_static_policy_list;
/*
* We manually invoke WITNESS_WARN() to allow Witness to generate
* warnings even if we don't end up ever triggering the wait at
* run-time. The consumer of the exclusive interface must not hold
* any locks (other than potentially Giant) since we may sleep for
* long (potentially indefinite) periods of time waiting for the
* framework to become quiescent so that a policy list change may
* be made.
* We manually invoke WITNESS_WARN() to allow Witness to generate warnings
* even if we don't end up ever triggering the wait at run-time. The
* consumer of the exclusive interface must not hold any locks (other than
* potentially Giant) since we may sleep for long (potentially indefinite)
* periods of time waiting for the framework to become quiescent so that a
* policy list change may be made.
*/
void
mac_policy_grab_exclusive(void)
@ -296,9 +317,9 @@ mac_init(void)
}
/*
* For the purposes of modules that want to know if they were loaded
* "early", set the mac_late flag once we've processed modules either
* linked into the kernel, or loaded before the kernel startup.
* For the purposes of modules that want to know if they were loaded "early",
* set the mac_late flag once we've processed modules either linked into the
* kernel, or loaded before the kernel startup.
*/
static void
mac_late_init(void)
@ -310,8 +331,8 @@ mac_late_init(void)
/*
* After the policy list has changed, walk the list to update any global
* flags. Currently, we support only one flag, and it's conditionally
* defined; as a result, the entire function is conditional. Eventually,
* the #else case might also iterate across the policies.
* defined; as a result, the entire function is conditional. Eventually, the
* #else case might also iterate across the policies.
*/
static void
mac_policy_updateflags(void)
@ -390,16 +411,16 @@ mac_policy_register(struct mac_policy_conf *mpc)
error = 0;
/*
* We don't technically need exclusive access while !mac_late,
* but hold it for assertion consistency.
* We don't technically need exclusive access while !mac_late, but
* hold it for assertion consistency.
*/
mac_policy_grab_exclusive();
/*
* If the module can potentially be unloaded, or we're loading
* late, we have to stick it in the non-static list and pay
* an extra performance overhead. Otherwise, we can pay a
* light locking cost and stick it in the static list.
* If the module can potentially be unloaded, or we're loading late,
* we have to stick it in the non-static list and pay an extra
* performance overhead. Otherwise, we can pay a light locking cost
* and stick it in the static list.
*/
static_entry = (!mac_late &&
!(mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK));
@ -432,18 +453,23 @@ mac_policy_register(struct mac_policy_conf *mpc)
mpc->mpc_runtime_flags |= MPC_RUNTIME_FLAG_REGISTERED;
/*
* If we're loading a MAC module after the framework has
* initialized, it has to go into the dynamic list. If
* we're loading it before we've finished initializing,
* it can go into the static list with weaker locker
* requirements.
* If we're loading a MAC module after the framework has initialized,
* it has to go into the dynamic list. If we're loading it before
* we've finished initializing, it can go into the static list with
* weaker locker requirements.
*/
if (static_entry)
LIST_INSERT_HEAD(&mac_static_policy_list, mpc, mpc_list);
else
LIST_INSERT_HEAD(&mac_policy_list, mpc, mpc_list);
/* Per-policy initialization. */
/*
* Per-policy initialization. Currently, this takes place under the
* exclusive lock, so policies must not sleep in their init method.
* In the future, we may want to separate "init" from "start", with
* "init" occuring without the lock held. Likewise, on tear-down,
* breaking out "stop" from "destroy".
*/
if (mpc->mpc_ops->mpo_init != NULL)
(*(mpc->mpc_ops->mpo_init))(mpc);
mac_policy_updateflags();
@ -461,9 +487,8 @@ mac_policy_unregister(struct mac_policy_conf *mpc)
{
/*
* If we fail the load, we may get a request to unload. Check
* to see if we did the run-time registration, and if not,
* silently succeed.
* If we fail the load, we may get a request to unload. Check to see
* if we did the run-time registration, and if not, silently succeed.
*/
mac_policy_grab_exclusive();
if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED) == 0) {
@ -480,8 +505,8 @@ mac_policy_unregister(struct mac_policy_conf *mpc)
}
#endif
/*
* Only allow the unload to proceed if the module is unloadable
* by its own definition.
* Only allow the unload to proceed if the module is unloadable by
* its own definition.
*/
if ((mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK) == 0) {
mac_policy_release_exclusive();
@ -710,8 +735,8 @@ __mac_set_proc(struct thread *td, struct __mac_set_proc_args *uap)
p->p_ucred = newcred;
/*
* Grab additional reference for use while revoking mmaps, prior
* to releasing the proc lock and sharing the cred.
* Grab additional reference for use while revoking mmaps, prior to
* releasing the proc lock and sharing the cred.
*/
crhold(newcred);
PROC_UNLOCK(p);