Merge tag 'audit-pr-20180403' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit

Pull audit updates from Paul Moore:
 "We didn't have anything to send for v4.16, but we're back with a
  little more than usual for v4.17.

  Eleven patches in total, most fall into the small fix category, but
  there are three non-trivial changes worth calling out:

   - the audit entry filter is being removed after deprecating it for
     quite a while (years of no one really using it because it turns out
     to be not very practical)

   - created our own version of "__mutex_owner()" because the locking
     folks were upset we were using theirs

   - improved our handling of kernel command line parameters to make
     them more forgiving

   - we fixed auditing of symlink operations

  Everything passes the audit-testsuite and as of a few minutes ago it
  merges well with your tree"

* tag 'audit-pr-20180403' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit:
  audit: add refused symlink to audit_names
  audit: remove path param from link denied function
  audit: link denied should not directly generate PATH record
  audit: make ANOM_LINK obey audit_enabled and audit_dummy_context
  audit: do not panic on invalid boot parameter
  audit: track the owner of the command mutex ourselves
  audit: return on memory error to avoid null pointer dereference
  audit: bail before bug check if audit disabled
  audit: deprecate the AUDIT_FILTER_ENTRY filter
  audit: session ID should not set arch quick field pointer
  audit: update bugtracker and source URIs

5 files changed, 94 insertions, 52 deletions

diff --git a/kernel/audit.c b/kernel/audit.c
index d97e8f0f73ca..670665c6e2a6 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -38,7 +38,8 @@
  *	  6) Support low-overhead kernel-based filtering to minimize the
  *	     information that must be passed to user-space.
  *
- * Example user-space utilities: http://people.redhat.com/sgrubb/audit/
+ * Audit userspace, documentation, tests, and bug/issue trackers:
+ * 	https://github.com/linux-audit
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
@@ -180,9 +181,21 @@ static char *audit_feature_names[2] = {
 	"loginuid_immutable",
 };
 
-
-/* Serialize requests from userspace. */
-DEFINE_MUTEX(audit_cmd_mutex);
+/**
+ * struct audit_ctl_mutex - serialize requests from userspace
+ * @lock: the mutex used for locking
+ * @owner: the task which owns the lock
+ *
+ * Description:
+ * This is the lock struct used to ensure we only process userspace requests
+ * in an orderly fashion.  We can't simply use a mutex/lock here because we
+ * need to track lock ownership so we don't end up blocking the lock owner in
+ * audit_log_start() or similar.
+ */
+static struct audit_ctl_mutex {
+	struct mutex lock;
+	void *owner;
+} audit_cmd_mutex;
 
 /* AUDIT_BUFSIZ is the size of the temporary buffer used for formatting
  * audit records.  Since printk uses a 1024 byte buffer, this buffer
@@ -227,6 +240,36 @@ int auditd_test_task(struct task_struct *task)
 }
 
 /**
+ * audit_ctl_lock - Take the audit control lock
+ */
+void audit_ctl_lock(void)
+{
+	mutex_lock(&audit_cmd_mutex.lock);
+	audit_cmd_mutex.owner = current;
+}
+
+/**
+ * audit_ctl_unlock - Drop the audit control lock
+ */
+void audit_ctl_unlock(void)
+{
+	audit_cmd_mutex.owner = NULL;
+	mutex_unlock(&audit_cmd_mutex.lock);
+}
+
+/**
+ * audit_ctl_owner_current - Test to see if the current task owns the lock
+ *
+ * Description:
+ * Return true if the current task owns the audit control lock, false if it
+ * doesn't own the lock.
+ */
+static bool audit_ctl_owner_current(void)
+{
+	return (current == audit_cmd_mutex.owner);
+}
+
+/**
  * auditd_pid_vnr - Return the auditd PID relative to the namespace
  *
  * Description:
@@ -860,8 +903,8 @@ int audit_send_list(void *_dest)
 	struct sock *sk = audit_get_sk(dest->net);
 
 	/* wait for parent to finish and send an ACK */
-	mutex_lock(&audit_cmd_mutex);
-	mutex_unlock(&audit_cmd_mutex);
+	audit_ctl_lock();
+	audit_ctl_unlock();
 
 	while ((skb = __skb_dequeue(&dest->q)) != NULL)
 		netlink_unicast(sk, skb, dest->portid, 0);
@@ -902,8 +945,8 @@ static int audit_send_reply_thread(void *arg)
 	struct audit_reply *reply = (struct audit_reply *)arg;
 	struct sock *sk = audit_get_sk(reply->net);
 
-	mutex_lock(&audit_cmd_mutex);
-	mutex_unlock(&audit_cmd_mutex);
+	audit_ctl_lock();
+	audit_ctl_unlock();
 
 	/* Ignore failure. It'll only happen if the sender goes away,
 	   because our timeout is set to infinite. */
@@ -1058,6 +1101,8 @@ static void audit_log_feature_change(int which, u32 old_feature, u32 new_feature
 		return;
 
 	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_FEATURE_CHANGE);
+	if (!ab)
+		return;
 	audit_log_task_info(ab, current);
 	audit_log_format(ab, " feature=%s old=%u new=%u old_lock=%u new_lock=%u res=%d",
 			 audit_feature_names[which], !!old_feature, !!new_feature,
@@ -1466,7 +1511,7 @@ static void audit_receive(struct sk_buff  *skb)
 	nlh = nlmsg_hdr(skb);
 	len = skb->len;
 
-	mutex_lock(&audit_cmd_mutex);
+	audit_ctl_lock();
 	while (nlmsg_ok(nlh, len)) {
 		err = audit_receive_msg(skb, nlh);
 		/* if err or if this message says it wants a response */
@@ -1475,7 +1520,7 @@ static void audit_receive(struct sk_buff  *skb)
 
 		nlh = nlmsg_next(nlh, &len);
 	}
-	mutex_unlock(&audit_cmd_mutex);
+	audit_ctl_unlock();
 }
 
 /* Run custom bind function on netlink socket group connect or bind requests. */
@@ -1547,6 +1592,9 @@ static int __init audit_init(void)
 	for (i = 0; i < AUDIT_INODE_BUCKETS; i++)
 		INIT_LIST_HEAD(&audit_inode_hash[i]);
 
+	mutex_init(&audit_cmd_mutex.lock);
+	audit_cmd_mutex.owner = NULL;
+
 	pr_info("initializing netlink subsys (%s)\n",
 		audit_default ? "enabled" : "disabled");
 	register_pernet_subsys(&audit_net_ops);
@@ -1567,19 +1615,26 @@ static int __init audit_init(void)
 }
 postcore_initcall(audit_init);
 
-/* Process kernel command-line parameter at boot time.  audit=0 or audit=1. */
+/*
+ * Process kernel command-line parameter at boot time.
+ * audit={0|off} or audit={1|on}.
+ */
 static int __init audit_enable(char *str)
 {
-	long val;
-
-	if (kstrtol(str, 0, &val))
-		panic("audit: invalid 'audit' parameter value (%s)\n", str);
-	audit_default = (val ? AUDIT_ON : AUDIT_OFF);
+	if (!strcasecmp(str, "off") || !strcmp(str, "0"))
+		audit_default = AUDIT_OFF;
+	else if (!strcasecmp(str, "on") || !strcmp(str, "1"))
+		audit_default = AUDIT_ON;
+	else {
+		pr_err("audit: invalid 'audit' parameter value (%s)\n", str);
+		audit_default = AUDIT_ON;
+	}
 
 	if (audit_default == AUDIT_OFF)
 		audit_initialized = AUDIT_DISABLED;
 	if (audit_set_enabled(audit_default))
-		panic("audit: error setting audit state (%d)\n", audit_default);
+		pr_err("audit: error setting audit state (%d)\n",
+		       audit_default);
 
 	pr_info("%s\n", audit_default ?
 		"enabled (after initialization)" : "disabled (until reboot)");
@@ -1710,8 +1765,7 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
 	 *    using a PID anchored in the caller's namespace
 	 * 2. generator holding the audit_cmd_mutex - we don't want to block
 	 *    while holding the mutex */
-	if (!(auditd_test_task(current) ||
-	      (current == __mutex_owner(&audit_cmd_mutex)))) {
+	if (!(auditd_test_task(current) || audit_ctl_owner_current())) {
 		long stime = audit_backlog_wait_time;
 
 		while (audit_backlog_limit &&
@@ -2254,33 +2308,23 @@ EXPORT_SYMBOL(audit_log_task_info);
 /**
  * audit_log_link_denied - report a link restriction denial
  * @operation: specific link operation
- * @link: the path that triggered the restriction
  */
-void audit_log_link_denied(const char *operation, const struct path *link)
+void audit_log_link_denied(const char *operation)
 {
 	struct audit_buffer *ab;
-	struct audit_names *name;
 
-	name = kzalloc(sizeof(*name), GFP_NOFS);
-	if (!name)
+	if (!audit_enabled || audit_dummy_context())
 		return;
 
 	/* Generate AUDIT_ANOM_LINK with subject, operation, outcome. */
 	ab = audit_log_start(current->audit_context, GFP_KERNEL,
 			     AUDIT_ANOM_LINK);
 	if (!ab)
-		goto out;
+		return;
 	audit_log_format(ab, "op=%s", operation);
 	audit_log_task_info(ab, current);
 	audit_log_format(ab, " res=0");
 	audit_log_end(ab);
-
-	/* Generate AUDIT_PATH record with object. */
-	name->type = AUDIT_TYPE_NORMAL;
-	audit_copy_inode(name, link->dentry, d_backing_inode(link->dentry));
-	audit_log_name(current->audit_context, name, link, 0, NULL);
-out:
-	kfree(name);
 }
 
 /**
diff --git a/kernel/audit.h b/kernel/audit.h
index af5bc59487ed..214e14948370 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -341,4 +341,5 @@ extern struct list_head *audit_killed_trees(void);
 #define audit_filter_inodes(t,c) AUDIT_DISABLED
 #endif
 
-extern struct mutex audit_cmd_mutex;
+extern void audit_ctl_lock(void);
+extern void audit_ctl_unlock(void);
diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index fd353120e0d9..67e6956c0b61 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -709,7 +709,7 @@ static int prune_tree_thread(void *unused)
 			schedule();
 		}
 
-		mutex_lock(&audit_cmd_mutex);
+		audit_ctl_lock();
 		mutex_lock(&audit_filter_mutex);
 
 		while (!list_empty(&prune_list)) {
@@ -727,7 +727,7 @@ static int prune_tree_thread(void *unused)
 		}
 
 		mutex_unlock(&audit_filter_mutex);
-		mutex_unlock(&audit_cmd_mutex);
+		audit_ctl_unlock();
 	}
 	return 0;
 }
@@ -924,7 +924,7 @@ static void audit_schedule_prune(void)
  */
 void audit_kill_trees(struct list_head *list)
 {
-	mutex_lock(&audit_cmd_mutex);
+	audit_ctl_lock();
 	mutex_lock(&audit_filter_mutex);
 
 	while (!list_empty(list)) {
@@ -942,7 +942,7 @@ void audit_kill_trees(struct list_head *list)
 	}
 
 	mutex_unlock(&audit_filter_mutex);
-	mutex_unlock(&audit_cmd_mutex);
+	audit_ctl_unlock();
 }
 
 /*
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index 4a1758adb222..d7a807e81451 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -258,8 +258,8 @@ static inline struct audit_entry *audit_to_entry_common(struct audit_rule_data *
 		goto exit_err;
 #ifdef CONFIG_AUDITSYSCALL
 	case AUDIT_FILTER_ENTRY:
-		if (rule->action == AUDIT_ALWAYS)
-			goto exit_err;
+		pr_err("AUDIT_FILTER_ENTRY is deprecated\n");
+		goto exit_err;
 	case AUDIT_FILTER_EXIT:
 	case AUDIT_FILTER_TASK:
 #endif
@@ -496,7 +496,6 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
 			if (!gid_valid(f->gid))
 				goto exit_free;
 			break;
-		case AUDIT_SESSIONID:
 		case AUDIT_ARCH:
 			entry->rule.arch_f = f;
 			break;
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index e80459f7e132..4e0a4ac803db 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1511,30 +1511,28 @@ void __audit_syscall_entry(int major, unsigned long a1, unsigned long a2,
 	struct audit_context *context = tsk->audit_context;
 	enum audit_state     state;
 
-	if (!context)
+	if (!audit_enabled || !context)
 		return;
 
 	BUG_ON(context->in_syscall || context->name_count);
 
-	if (!audit_enabled)
+	state = context->state;
+	if (state == AUDIT_DISABLED)
 		return;
 
+	context->dummy = !audit_n_rules;
+	if (!context->dummy && state == AUDIT_BUILD_CONTEXT) {
+		context->prio = 0;
+		if (auditd_test_task(tsk))
+			return;
+	}
+
 	context->arch	    = syscall_get_arch();
 	context->major      = major;
 	context->argv[0]    = a1;
 	context->argv[1]    = a2;
 	context->argv[2]    = a3;
 	context->argv[3]    = a4;
-
-	state = context->state;
-	context->dummy = !audit_n_rules;
-	if (!context->dummy && state == AUDIT_BUILD_CONTEXT) {
-		context->prio = 0;
-		state = audit_filter_syscall(tsk, context, &audit_filter_list[AUDIT_FILTER_ENTRY]);
-	}
-	if (state == AUDIT_DISABLED)
-		return;
-
 	context->serial     = 0;
 	context->ctime = current_kernel_time64();
 	context->in_syscall = 1;