audit: clean simple fsnotify implementation

This is to be used to audit by executable path rules, but audit watches should
be able to share this code eventually.

At the moment the audit watch code is a lot more complex.  That code only
creates one fsnotify watch per parent directory.  That 'audit_parent' in
turn has a list of 'audit_watches' which contain the name, ino, dev of
the specific object we care about.  This just creates one fsnotify watch
per object we care about.  So if you watch 100 inodes in /etc this code
will create 100 fsnotify watches on /etc.  The audit_watch code will
instead create 1 fsnotify watch on /etc (the audit_parent) and then 100
individual watches chained from that fsnotify mark.

We should be able to convert the audit_watch code to do one fsnotify
mark per watch and simplify things/remove a whole lot of code.  After
that conversion we should be able to convert the audit_fsnotify code to
support that hierarchy if the optimization is necessary.

Move the access to the entry for audit_match_signal() to the beginning of
the audit_del_rule() function in case the entry found is the same one passed
in.  This will enable it to be used by audit_autoremove_mark_rule(),
kill_rules() and audit_remove_parent_watches().

This is a heavily modified and merged version of two patches originally
submitted by Eric Paris.

Cc: Peter Moody <[email protected]>
Cc: Eric Paris <[email protected]>
Signed-off-by: Richard Guy Briggs <[email protected]>
[PM: added a space after a declaration to keep ./scripts/checkpatch happy]
Signed-off-by: Paul Moore <[email protected]>

Author: rgbriggs

kernel/Makefile

@@ -62,7 +62,7 @@ obj-$(CONFIG_SMP) += stop_machine.o
 obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o
 obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
 obj-$(CONFIG_AUDITSYSCALL) += auditsc.o
-obj-$(CONFIG_AUDIT_WATCH) += audit_watch.o
+obj-$(CONFIG_AUDIT_WATCH) += audit_watch.o audit_fsnotify.o
 obj-$(CONFIG_AUDIT_TREE) += audit_tree.o
 obj-$(CONFIG_GCOV_KERNEL) += gcov/
 obj-$(CONFIG_KPROBES) += kprobes.o

kernel/audit.h

@@ -50,6 +50,7 @@ enum audit_state {
 
 /* Rule lists */
 struct audit_watch;
+struct audit_fsnotify_mark;
 struct audit_tree;
 struct audit_chunk;
 
@@ -252,6 +253,7 @@ struct audit_net {
 extern int selinux_audit_rule_update(void);
 
 extern struct mutex audit_filter_mutex;
+extern int audit_del_rule(struct audit_entry *);
 extern void audit_free_rule_rcu(struct rcu_head *);
 extern struct list_head audit_filter_list[];
 
@@ -266,6 +268,13 @@ extern int audit_add_watch(struct audit_krule *krule, struct list_head **list);
 extern void audit_remove_watch_rule(struct audit_krule *krule);
 extern char *audit_watch_path(struct audit_watch *watch);
 extern int audit_watch_compare(struct audit_watch *watch, unsigned long ino, dev_t dev);
+
+extern struct audit_fsnotify_mark *audit_alloc_mark(struct audit_krule *krule, char *pathname, int len);
+extern char *audit_mark_path(struct audit_fsnotify_mark *mark);
+extern void audit_remove_mark(struct audit_fsnotify_mark *audit_mark);
+extern void audit_remove_mark_rule(struct audit_krule *krule);
+extern int audit_mark_compare(struct audit_fsnotify_mark *mark, unsigned long ino, dev_t dev);
+
 #else
 #define audit_put_watch(w) {}
 #define audit_get_watch(w) {}
@@ -275,6 +284,11 @@ extern int audit_watch_compare(struct audit_watch *watch, unsigned long ino, dev
 #define audit_watch_path(w) ""
 #define audit_watch_compare(w, i, d) 0
 
+#define audit_alloc_mark(k, p, l) (ERR_PTR(-EINVAL))
+#define audit_mark_path(m) ""
+#define audit_remove_mark(m)
+#define audit_remove_mark_rule(k)
+#define audit_mark_compare(m, i, d) 0
 #endif /* CONFIG_AUDIT_WATCH */
 
 #ifdef CONFIG_AUDIT_TREE

kernel/audit_fsnotify.c

@@ -0,0 +1,216 @@
+/* audit_fsnotify.c -- tracking inodes
+ *
+ * Copyright 2003-2009,2014-2015 Red Hat, Inc.
+ * Copyright 2005 Hewlett-Packard Development Company, L.P.
+ * Copyright 2005 IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/audit.h>
+#include <linux/kthread.h>
+#include <linux/mutex.h>
+#include <linux/fs.h>
+#include <linux/fsnotify_backend.h>
+#include <linux/namei.h>
+#include <linux/netlink.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/security.h>
+#include "audit.h"
+
+/*
+ * this mark lives on the parent directory of the inode in question.
+ * but dev, ino, and path are about the child
+ */
+struct audit_fsnotify_mark {
+	dev_t dev;		/* associated superblock device */
+	unsigned long ino;	/* associated inode number */
+	char *path;		/* insertion path */
+	struct fsnotify_mark mark; /* fsnotify mark on the inode */
+	struct audit_krule *rule;
+};
+
+/* fsnotify handle. */
+static struct fsnotify_group *audit_fsnotify_group;
+
+/* fsnotify events we care about. */
+#define AUDIT_FS_EVENTS (FS_MOVE | FS_CREATE | FS_DELETE | FS_DELETE_SELF |\
+			 FS_MOVE_SELF | FS_EVENT_ON_CHILD)
+
+static void audit_fsnotify_mark_free(struct audit_fsnotify_mark *audit_mark)
+{
+	kfree(audit_mark->path);
+	kfree(audit_mark);
+}
+
+static void audit_fsnotify_free_mark(struct fsnotify_mark *mark)
+{
+	struct audit_fsnotify_mark *audit_mark;
+
+	audit_mark = container_of(mark, struct audit_fsnotify_mark, mark);
+	audit_fsnotify_mark_free(audit_mark);
+}
+
+char *audit_mark_path(struct audit_fsnotify_mark *mark)
+{
+	return mark->path;
+}
+
+int audit_mark_compare(struct audit_fsnotify_mark *mark, unsigned long ino, dev_t dev)
+{
+	if (mark->ino == AUDIT_INO_UNSET)
+		return 0;
+	return (mark->ino == ino) && (mark->dev == dev);
+}
+
+static void audit_update_mark(struct audit_fsnotify_mark *audit_mark,
+			     struct inode *inode)
+{
+	audit_mark->dev = inode ? inode->i_sb->s_dev : AUDIT_DEV_UNSET;
+	audit_mark->ino = inode ? inode->i_ino : AUDIT_INO_UNSET;
+}
+
+struct audit_fsnotify_mark *audit_alloc_mark(struct audit_krule *krule, char *pathname, int len)
+{
+	struct audit_fsnotify_mark *audit_mark;
+	struct path path;
+	struct dentry *dentry;
+	struct inode *inode;
+	int ret;
+
+	if (pathname[0] != '/' || pathname[len-1] == '/')
+		return ERR_PTR(-EINVAL);
+
+	dentry = kern_path_locked(pathname, &path);
+	if (IS_ERR(dentry))
+		return (void *)dentry; /* returning an error */
+	inode = path.dentry->d_inode;
+	mutex_unlock(&inode->i_mutex);
+
+	audit_mark = kzalloc(sizeof(*audit_mark), GFP_KERNEL);
+	if (unlikely(!audit_mark)) {
+		audit_mark = ERR_PTR(-ENOMEM);
+		goto out;
+	}
+
+	fsnotify_init_mark(&audit_mark->mark, audit_fsnotify_free_mark);
+	audit_mark->mark.mask = AUDIT_FS_EVENTS;
+	audit_mark->path = pathname;
+	audit_update_mark(audit_mark, dentry->d_inode);
+	audit_mark->rule = krule;
+
+	ret = fsnotify_add_mark(&audit_mark->mark, audit_fsnotify_group, inode, NULL, true);
+	if (ret < 0) {
+		audit_fsnotify_mark_free(audit_mark);
+		audit_mark = ERR_PTR(ret);
+	}
+out:
+	dput(dentry);
+	path_put(&path);
+	return audit_mark;
+}
+
+static void audit_mark_log_rule_change(struct audit_fsnotify_mark *audit_mark, char *op)
+{
+	struct audit_buffer *ab;
+	struct audit_krule *rule = audit_mark->rule;
+
+	if (!audit_enabled)
+		return;
+	ab = audit_log_start(NULL, GFP_NOFS, AUDIT_CONFIG_CHANGE);
+	if (unlikely(!ab))
+		return;
+	audit_log_format(ab, "auid=%u ses=%u op=",
+			 from_kuid(&init_user_ns, audit_get_loginuid(current)),
+			 audit_get_sessionid(current));
+	audit_log_string(ab, op);
+	audit_log_format(ab, " path=");
+	audit_log_untrustedstring(ab, audit_mark->path);
+	audit_log_key(ab, rule->filterkey);
+	audit_log_format(ab, " list=%d res=1", rule->listnr);
+	audit_log_end(ab);
+}
+
+void audit_remove_mark(struct audit_fsnotify_mark *audit_mark)
+{
+	fsnotify_destroy_mark(&audit_mark->mark, audit_fsnotify_group);
+	fsnotify_put_mark(&audit_mark->mark);
+}
+
+void audit_remove_mark_rule(struct audit_krule *krule)
+{
+	struct audit_fsnotify_mark *mark = krule->exe;
+
+	audit_remove_mark(mark);
+}
+
+static void audit_autoremove_mark_rule(struct audit_fsnotify_mark *audit_mark)
+{
+	struct audit_krule *rule = audit_mark->rule;
+	struct audit_entry *entry = container_of(rule, struct audit_entry, rule);
+
+	audit_mark_log_rule_change(audit_mark, "autoremove_rule");
+	audit_del_rule(entry);
+}
+
+/* Update mark data in audit rules based on fsnotify events. */
+static int audit_mark_handle_event(struct fsnotify_group *group,
+				    struct inode *to_tell,
+				    struct fsnotify_mark *inode_mark,
+				    struct fsnotify_mark *vfsmount_mark,
+				    u32 mask, void *data, int data_type,
+				    const unsigned char *dname, u32 cookie)
+{
+	struct audit_fsnotify_mark *audit_mark;
+	struct inode *inode = NULL;
+
+	audit_mark = container_of(inode_mark, struct audit_fsnotify_mark, mark);
+
+	BUG_ON(group != audit_fsnotify_group);
+
+	switch (data_type) {
+	case (FSNOTIFY_EVENT_PATH):
+		inode = ((struct path *)data)->dentry->d_inode;
+		break;
+	case (FSNOTIFY_EVENT_INODE):
+		inode = (struct inode *)data;
+		break;
+	default:
+		BUG();
+		return 0;
+	};
+
+	if (mask & (FS_CREATE|FS_MOVED_TO|FS_DELETE|FS_MOVED_FROM)) {
+		if (audit_compare_dname_path(dname, audit_mark->path, AUDIT_NAME_FULL))
+			return 0;
+		audit_update_mark(audit_mark, inode);
+	} else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
+		audit_autoremove_mark_rule(audit_mark);
+
+	return 0;
+}
+
+static const struct fsnotify_ops audit_mark_fsnotify_ops = {
+	.handle_event =	audit_mark_handle_event,
+};
+
+static int __init audit_fsnotify_init(void)
+{
+	audit_fsnotify_group = fsnotify_alloc_group(&audit_mark_fsnotify_ops);
+	if (IS_ERR(audit_fsnotify_group)) {
+		audit_fsnotify_group = NULL;
+		audit_panic("cannot create audit fsnotify group");
+	}
+	return 0;
+}
+device_initcall(audit_fsnotify_init);

kernel/auditfilter.c

@@ -935,7 +935,7 @@ static inline int audit_add_rule(struct audit_entry *entry)
 }
 
 /* Remove an existing rule from filterlist. */
-static inline int audit_del_rule(struct audit_entry *entry)
+int audit_del_rule(struct audit_entry *entry)
 {
 	struct audit_entry  *e;
 	struct audit_tree *tree = entry->rule.tree;