[PATCH v2 1/2] LSM: switch to blocking policy update notifiers

[PATCH v2 1/2] LSM: switch to blocking policy update notifiers

[Janne Karhunen]

Atomic policy updaters are not very useful as they cannot
usually perform the policy updates on their own. Since it
seems that there is no strict need for the atomicity,
switch to the blocking variant. While doing so, rename
the functions accordingly.

Changelog v2
- Rebase to 'next-queued-testing'

Signed-off-by: Janne Karhunen <janne.karhunen@gmail.com>
Acked-by: Paul Moore <paul@paul-moore.com>
---
 drivers/infiniband/core/device.c |  6 +++---
 include/linux/security.h         |  6 +++---
 security/security.c              | 23 +++++++++++++----------
 security/selinux/hooks.c         |  2 +-
 security/selinux/selinuxfs.c     |  2 +-
 5 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
index 78dc07c6ac4b..61c0c93a2e73 100644
--- a/drivers/infiniband/core/device.c
+++ b/drivers/infiniband/core/device.c
@@ -2499,7 +2499,7 @@ static int __init ib_core_init(void)
 		goto err_mad;
 	}
 
-	ret = register_lsm_notifier(&ibdev_lsm_nb);
+	ret = register_blocking_lsm_notifier(&ibdev_lsm_nb);
 	if (ret) {
 		pr_warn("Couldn't register LSM notifier. ret %d\n", ret);
 		goto err_sa;
@@ -2518,7 +2518,7 @@ static int __init ib_core_init(void)
 	return 0;
 
 err_compat:
-	unregister_lsm_notifier(&ibdev_lsm_nb);
+	unregister_blocking_lsm_notifier(&ibdev_lsm_nb);
 err_sa:
 	ib_sa_cleanup();
 err_mad:
@@ -2544,7 +2544,7 @@ static void __exit ib_core_cleanup(void)
 	nldev_exit();
 	rdma_nl_unregister(RDMA_NL_LS);
 	unregister_pernet_device(&rdma_dev_net_ops);
-	unregister_lsm_notifier(&ibdev_lsm_nb);
+	unregister_blocking_lsm_notifier(&ibdev_lsm_nb);
 	ib_sa_cleanup();
 	ib_mad_cleanup();
 	addr_cleanup();
diff --git a/include/linux/security.h b/include/linux/security.h
index 659071c2e57c..fc655fbe44ad 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -189,9 +189,9 @@ static inline const char *kernel_load_data_id_str(enum kernel_load_data_id id)
 
 #ifdef CONFIG_SECURITY
 
-int call_lsm_notifier(enum lsm_event event, void *data);
-int register_lsm_notifier(struct notifier_block *nb);
-int unregister_lsm_notifier(struct notifier_block *nb);
+int call_blocking_lsm_notifier(enum lsm_event event, void *data);
+int register_blocking_lsm_notifier(struct notifier_block *nb);
+int unregister_blocking_lsm_notifier(struct notifier_block *nb);
 
 /* prototypes */
 extern int security_init(void);
diff --git a/security/security.c b/security/security.c
index 613a5c00e602..47e5849d7557 100644
--- a/security/security.c
+++ b/security/security.c
@@ -39,7 +39,7 @@
 #define LSM_COUNT (__end_lsm_info - __start_lsm_info)
 
 struct security_hook_heads security_hook_heads __lsm_ro_after_init;
-static ATOMIC_NOTIFIER_HEAD(lsm_notifier_chain);
+static BLOCKING_NOTIFIER_HEAD(blocking_lsm_notifier_chain);
 
 static struct kmem_cache *lsm_file_cache;
 static struct kmem_cache *lsm_inode_cache;
@@ -430,23 +430,26 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
 		panic("%s - Cannot get early memory.\n", __func__);
 }
 
-int call_lsm_notifier(enum lsm_event event, void *data)
+int call_blocking_lsm_notifier(enum lsm_event event, void *data)
 {
-	return atomic_notifier_call_chain(&lsm_notifier_chain, event, data);
+	return blocking_notifier_call_chain(&blocking_lsm_notifier_chain,
+					    event, data);
 }
-EXPORT_SYMBOL(call_lsm_notifier);
+EXPORT_SYMBOL(call_blocking_lsm_notifier);
 
-int register_lsm_notifier(struct notifier_block *nb)
+int register_blocking_lsm_notifier(struct notifier_block *nb)
 {
-	return atomic_notifier_chain_register(&lsm_notifier_chain, nb);
+	return blocking_notifier_chain_register(&blocking_lsm_notifier_chain,
+						nb);
 }
-EXPORT_SYMBOL(register_lsm_notifier);
+EXPORT_SYMBOL(register_blocking_lsm_notifier);
 
-int unregister_lsm_notifier(struct notifier_block *nb)
+int unregister_blocking_lsm_notifier(struct notifier_block *nb)
 {
-	return atomic_notifier_chain_unregister(&lsm_notifier_chain, nb);
+	return blocking_notifier_chain_unregister(&blocking_lsm_notifier_chain,
+						  nb);
 }
-EXPORT_SYMBOL(unregister_lsm_notifier);
+EXPORT_SYMBOL(unregister_blocking_lsm_notifier);
 
 /**
  * lsm_cred_alloc - allocate a composite cred blob
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index c61787b15f27..c1e37018c8eb 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -197,7 +197,7 @@ static int selinux_lsm_notifier_avc_callback(u32 event)
 {
 	if (event == AVC_CALLBACK_RESET) {
 		sel_ib_pkey_flush();
-		call_lsm_notifier(LSM_POLICY_CHANGE, NULL);
+		call_blocking_lsm_notifier(LSM_POLICY_CHANGE, NULL);
 	}
 
 	return 0;
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 145ee62f205a..1e2e3e4b5fdb 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -180,7 +180,7 @@ static ssize_t sel_write_enforce(struct file *file, const char __user *buf,
 		selnl_notify_setenforce(new_value);
 		selinux_status_update_setenforce(state, new_value);
 		if (!new_value)
-			call_lsm_notifier(LSM_POLICY_CHANGE, NULL);
+			call_blocking_lsm_notifier(LSM_POLICY_CHANGE, NULL);
 	}
 	length = count;
 out:
-- 
2.17.1

[PATCH v2 1/2] ima: use the lsm policy update notifier

[Janne Karhunen]

Don't do lazy policy updates while running the rule matching,
run the updates as they happen.

Depends on commit 141a61ce6c60 ("LSM: switch to blocking policy update notifiers")

Changelog v2
- Rebase to 'next-queued-testing'
- Use memset to initialize the lsm rule array
- Don't duplicate elements that are immutable during the rule copy

=========
Signed-off-by: Janne Karhunen <janne.karhunen@gmail.com>
---
 security/integrity/ima/ima.h        |   2 +
 security/integrity/ima/ima_main.c   |   8 ++
 security/integrity/ima/ima_policy.c | 116 +++++++++++++++++++++++-----
 3 files changed, 106 insertions(+), 20 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 18b48a6d0b80..579544527246 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -155,6 +155,8 @@ unsigned long ima_get_binary_runtime_size(void);
 int ima_init_template(void);
 void ima_init_template_list(void);
 int __init ima_init_digests(void);
+int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
+			  void *lsm_data);
 
 /*
  * used to protect h_table and sha_table
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index af341a80118f..a7e7e2d7224c 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -43,6 +43,10 @@ int ima_appraise;
 int ima_hash_algo = HASH_ALGO_SHA1;
 static int hash_setup_done;
 
+static struct notifier_block ima_lsm_policy_notifier = {
+	.notifier_call = ima_lsm_policy_change,
+};
+
 static int __init hash_setup(char *str)
 {
 	struct ima_template_desc *template_desc = ima_template_desc_current();
@@ -622,6 +626,10 @@ static int __init init_ima(void)
 		error = ima_init();
 	}
 
+	error = register_blocking_lsm_notifier(&ima_lsm_policy_notifier);
+	if (error)
+		pr_warn("Couldn't register LSM notifier, error %d\n", error);
+
 	if (!error)
 		ima_update_policy_flag();
 
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index fd9b01881d17..e1550859f870 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -250,31 +250,113 @@ static int __init default_appraise_policy_setup(char *str)
 }
 __setup("ima_appraise_tcb", default_appraise_policy_setup);
 
+static void ima_lsm_free_rule(struct ima_rule_entry *entry)
+{
+	int i;
+
+	for (i = 0; i < MAX_LSM_RULES; i++) {
+		kfree(entry->lsm[i].rule);
+		kfree(entry->lsm[i].args_p);
+	}
+	kfree(entry);
+}
+
+static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry)
+{
+	struct ima_rule_entry *nentry;
+	int i, result;
+
+	nentry = kmalloc(sizeof(*nentry), GFP_KERNEL);
+	if (!nentry)
+		return NULL;
+
+	/*
+	 * Immutable elements are copied over as pointers and data; only
+	 * lsm rules can change
+	 */
+	memcpy(nentry, entry, sizeof(*nentry));
+	memset(nentry->lsm, 0, FIELD_SIZEOF(struct ima_rule_entry, lsm));
+
+	for (i = 0; i < MAX_LSM_RULES; i++) {
+		if (!entry->lsm[i].rule)
+			continue;
+
+		nentry->lsm[i].type = entry->lsm[i].type;
+		nentry->lsm[i].args_p = kstrdup(entry->lsm[i].args_p,
+						GFP_KERNEL);
+		if (!nentry->lsm[i].args_p)
+			goto out_err;
+
+		result = security_filter_rule_init(nentry->lsm[i].type,
+						   Audit_equal,
+						   nentry->lsm[i].args_p,
+						   &nentry->lsm[i].rule);
+		if (result == -EINVAL)
+			pr_warn("ima: rule for LSM \'%d\' is undefined\n",
+				entry->lsm[i].type);
+	}
+	return nentry;
+
+out_err:
+	ima_lsm_free_rule(nentry);
+	return NULL;
+}
+
+static int ima_lsm_update_rule(struct ima_rule_entry *entry)
+{
+	struct ima_rule_entry *nentry;
+
+	nentry = ima_lsm_copy_rule(entry);
+	if (!nentry)
+		return -ENOMEM;
+
+	list_replace_rcu(&entry->list, &nentry->list);
+	synchronize_rcu();
+	ima_lsm_free_rule(entry);
+
+	return 0;
+}
+
 /*
  * The LSM policy can be reloaded, leaving the IMA LSM based rules referring
  * to the old, stale LSM policy.  Update the IMA LSM based rules to reflect
- * the reloaded LSM policy.  We assume the rules still exist; and BUG_ON() if
- * they don't.
+ * the reloaded LSM policy.
  */
 static void ima_lsm_update_rules(void)
 {
-	struct ima_rule_entry *entry;
-	int result;
-	int i;
+	struct ima_rule_entry *entry, *e;
+	int i, result, needs_update;
 
-	list_for_each_entry(entry, &ima_policy_rules, list) {
+	list_for_each_entry_safe(entry, e, &ima_policy_rules, list) {
+		needs_update = 0;
 		for (i = 0; i < MAX_LSM_RULES; i++) {
-			if (!entry->lsm[i].rule)
-				continue;
-			result = security_filter_rule_init(entry->lsm[i].type,
-							   Audit_equal,
-							   entry->lsm[i].args_p,
-							   &entry->lsm[i].rule);
-			BUG_ON(!entry->lsm[i].rule);
+			if (entry->lsm[i].rule) {
+				needs_update = 1;
+				break;
+			}
+		}
+		if (!needs_update)
+			continue;
+
+		result = ima_lsm_update_rule(entry);
+		if (result) {
+			pr_err("ima: lsm rule update error %d\n",
+				result);
+			return;
 		}
 	}
 }
 
+int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
+			  void *lsm_data)
+{
+	if (event != LSM_POLICY_CHANGE)
+		return NOTIFY_DONE;
+
+	ima_lsm_update_rules();
+	return NOTIFY_OK;
+}
+
 /**
  * ima_match_rules - determine whether an inode matches the measure rule.
  * @rule: a pointer to a rule
@@ -328,11 +410,10 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
 	for (i = 0; i < MAX_LSM_RULES; i++) {
 		int rc = 0;
 		u32 osid;
-		int retried = 0;
 
 		if (!rule->lsm[i].rule)
 			continue;
-retry:
+
 		switch (i) {
 		case LSM_OBJ_USER:
 		case LSM_OBJ_ROLE:
@@ -353,11 +434,6 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
 		default:
 			break;
 		}
-		if ((rc < 0) && (!retried)) {
-			retried = 1;
-			ima_lsm_update_rules();
-			goto retry;
-		}
 		if (!rc)
 			return false;
 	}
-- 
2.17.1

Re: [PATCH v2 1/2] ima: use the lsm policy update notifier

[Mimi Zohar]

On Wed, 2019-06-12 at 10:44 +0300, Janne Karhunen wrote:
> Don't do lazy policy updates while running the rule matching,
> run the updates as they happen.
> 
> Depends on commit 141a61ce6c60 ("LSM: switch to blocking policy update notifiers")
> 
> Changelog v2
> - Rebase to 'next-queued-testing'
> - Use memset to initialize the lsm rule array
> - Don't duplicate elements that are immutable during the rule copy
> 
> =========
> Signed-off-by: Janne Karhunen <janne.karhunen@gmail.com>
> 

Thanks, this looks a lot better.

Mimi

Re: [PATCH v2 1/2] LSM: switch to blocking policy update notifiers

[Mimi Zohar]

Hi Paul,

On Wed, 2019-06-12 at 10:44 +0300, Janne Karhunen wrote:
> Atomic policy updaters are not very useful as they cannot
> usually perform the policy updates on their own. Since it
> seems that there is no strict need for the atomicity,
> switch to the blocking variant. While doing so, rename
> the functions accordingly.
> 
> Changelog v2
> - Rebase to 'next-queued-testing'
> 
> Signed-off-by: Janne Karhunen <janne.karhunen@gmail.com>
> Acked-by: Paul Moore <paul@paul-moore.com>

The patches need to be upstreamed together.  Do you have any problems
with my upstreaming them via linux-integrity?

Mimi

Re: [PATCH v2 1/2] LSM: switch to blocking policy update notifiers

[Paul Moore]

On Wed, Jun 12, 2019 at 9:28 AM Mimi Zohar <zohar@linux.ibm.com> wrote:
> Hi Paul,

/me waves

> On Wed, 2019-06-12 at 10:44 +0300, Janne Karhunen wrote:
> > Atomic policy updaters are not very useful as they cannot
> > usually perform the policy updates on their own. Since it
> > seems that there is no strict need for the atomicity,
> > switch to the blocking variant. While doing so, rename
> > the functions accordingly.
> >
> > Changelog v2
> > - Rebase to 'next-queued-testing'
> >
> > Signed-off-by: Janne Karhunen <janne.karhunen@gmail.com>
> > Acked-by: Paul Moore <paul@paul-moore.com>
>
> The patches need to be upstreamed together.  Do you have any problems
> with my upstreaming them via linux-integrity?

Nope, I've been operating under the assumption that you would be
taking both patches via the linux-integrity tree.

-- 
paul moore
www.paul-moore.com

Re: [PATCH v2 1/2] LSM: switch to blocking policy update notifiers

[James Morris]

On Wed, 12 Jun 2019, Janne Karhunen wrote:

> Atomic policy updaters are not very useful as they cannot
> usually perform the policy updates on their own. Since it
> seems that there is no strict need for the atomicity,
> switch to the blocking variant. While doing so, rename
> the functions accordingly.
> 
> Changelog v2
> - Rebase to 'next-queued-testing'
> 
> Signed-off-by: Janne Karhunen <janne.karhunen@gmail.com>
> Acked-by: Paul Moore <paul@paul-moore.com>


Acked-by: James Morris <jamorris@linux.microsoft.com>

-- 
James Morris
<jmorris@namei.org>