audit: seperate audit inode watches into a subfile

In preparation for converting audit to use fsnotify instead of inotify we
seperate the inode watching code into it's own file.  This is similar to
how the audit tree watching code is already seperated into audit_tree.c

Signed-off-by: Eric Paris <eparis@redhat.com>

1 files changed, 534 insertions, 0 deletions

diff --git a/kernel/audit_watch.c b/kernel/audit_watch.c
new file mode 100644
index 000000000000..da8be6d39c1a
--- /dev/null
+++ b/kernel/audit_watch.c
@@ -0,0 +1,534 @@
+/* audit_watch.c -- watching inodes
+ *
+ * Copyright 2003-2009 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/audit.h>
+#include <linux/kthread.h>
+#include <linux/mutex.h>
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/netlink.h>
+#include <linux/sched.h>
+#include <linux/inotify.h>
+#include <linux/security.h>
+#include "audit.h"
+
+/*
+ * Reference counting:
+ *
+ * audit_parent: lifetime is from audit_init_parent() to receipt of an IN_IGNORED
+ *      event.  Each audit_watch holds a reference to its associated parent.
+ *
+ * audit_watch: if added to lists, lifetime is from audit_init_watch() to
+ *      audit_remove_watch().  Additionally, an audit_watch may exist
+ *      temporarily to assist in searching existing filter data.  Each
+ *      audit_krule holds a reference to its associated watch.
+ */
+
+struct audit_watch {
+        atomic_t                count;  /* reference count */
+        char                    *path;  /* insertion path */
+        dev_t                   dev;    /* associated superblock device */
+        unsigned long           ino;    /* associated inode number */
+        struct audit_parent     *parent; /* associated parent */
+        struct list_head        wlist;  /* entry in parent->watches list */
+        struct list_head        rules;  /* associated rules */
+};
+
+struct audit_parent {
+        struct list_head        ilist;  /* entry in inotify registration list */
+        struct list_head        watches; /* associated watches */
+        struct inotify_watch    wdata;  /* inotify watch data */
+        unsigned                flags;  /* status flags */
+};
+
+/* Inotify handle. */
+struct inotify_handle *audit_ih;
+
+/*
+ * audit_parent status flags:
+ *
+ * AUDIT_PARENT_INVALID - set anytime rules/watches are auto-removed due to
+ * a filesystem event to ensure we're adding audit watches to a valid parent.
+ * Technically not needed for IN_DELETE_SELF or IN_UNMOUNT events, as we cannot
+ * receive them while we have nameidata, but must be used for IN_MOVE_SELF which
+ * we can receive while holding nameidata.
+ */
+#define AUDIT_PARENT_INVALID    0x001
+
+/* Inotify events we care about. */
+#define AUDIT_IN_WATCH IN_MOVE|IN_CREATE|IN_DELETE|IN_DELETE_SELF|IN_MOVE_SELF
+
+static void audit_free_parent(struct inotify_watch *i_watch)
+{
+        struct audit_parent *parent;
+
+        parent = container_of(i_watch, struct audit_parent, wdata);
+        WARN_ON(!list_empty(&parent->watches));
+        kfree(parent);
+}
+
+void audit_get_watch(struct audit_watch *watch)
+{
+        atomic_inc(&watch->count);
+}
+
+void audit_put_watch(struct audit_watch *watch)
+{
+        if (atomic_dec_and_test(&watch->count)) {
+                WARN_ON(watch->parent);
+                WARN_ON(!list_empty(&watch->rules));
+                kfree(watch->path);
+                kfree(watch);
+        }
+}
+
+void audit_remove_watch(struct audit_watch *watch)
+{
+        list_del(&watch->wlist);
+        put_inotify_watch(&watch->parent->wdata);
+        watch->parent = NULL;
+        audit_put_watch(watch); /* match initial get */
+}
+
+char *audit_watch_path(struct audit_watch *watch)
+{
+        return watch->path;
+}
+
+struct list_head *audit_watch_rules(struct audit_watch *watch)
+{
+        return &watch->rules;
+}
+
+unsigned long audit_watch_inode(struct audit_watch *watch)
+{
+        return watch->ino;
+}
+
+dev_t audit_watch_dev(struct audit_watch *watch)
+{
+        return watch->dev;
+}
+
+/* Initialize a parent watch entry. */
+static struct audit_parent *audit_init_parent(struct nameidata *ndp)
+{
+        struct audit_parent *parent;
+        s32 wd;
+
+        parent = kzalloc(sizeof(*parent), GFP_KERNEL);
+        if (unlikely(!parent))
+                return ERR_PTR(-ENOMEM);
+
+        INIT_LIST_HEAD(&parent->watches);
+        parent->flags = 0;
+
+        inotify_init_watch(&parent->wdata);
+        /* grab a ref so inotify watch hangs around until we take audit_filter_mutex */
+        get_inotify_watch(&parent->wdata);
+        wd = inotify_add_watch(audit_ih, &parent->wdata,
+                               ndp->path.dentry->d_inode, AUDIT_IN_WATCH);
+        if (wd < 0) {
+                audit_free_parent(&parent->wdata);
+                return ERR_PTR(wd);
+        }
+
+        return parent;
+}
+
+/* Initialize a watch entry. */
+static struct audit_watch *audit_init_watch(char *path)
+{
+        struct audit_watch *watch;
+
+        watch = kzalloc(sizeof(*watch), GFP_KERNEL);
+        if (unlikely(!watch))
+                return ERR_PTR(-ENOMEM);
+
+        INIT_LIST_HEAD(&watch->rules);
+        atomic_set(&watch->count, 1);
+        watch->path = path;
+        watch->dev = (dev_t)-1;
+        watch->ino = (unsigned long)-1;
+
+        return watch;
+}
+
+/* Translate a watch string to kernel respresentation. */
+int audit_to_watch(struct audit_krule *krule, char *path, int len, u32 op)
+{
+        struct audit_watch *watch;
+
+        if (!audit_ih)
+                return -EOPNOTSUPP;
+
+        if (path[0] != '/' || path[len-1] == '/' ||
+            krule->listnr != AUDIT_FILTER_EXIT ||
+            op != Audit_equal ||
+            krule->inode_f || krule->watch || krule->tree)
+                return -EINVAL;
+
+        watch = audit_init_watch(path);
+        if (IS_ERR(watch))
+                return PTR_ERR(watch);
+
+        audit_get_watch(watch);
+        krule->watch = watch;
+
+        return 0;
+}
+
+/* Duplicate the given audit watch.  The new watch's rules list is initialized
+ * to an empty list and wlist is undefined. */
+static struct audit_watch *audit_dupe_watch(struct audit_watch *old)
+{
+        char *path;
+        struct audit_watch *new;
+
+        path = kstrdup(old->path, GFP_KERNEL);
+        if (unlikely(!path))
+                return ERR_PTR(-ENOMEM);
+
+        new = audit_init_watch(path);
+        if (IS_ERR(new)) {
+                kfree(path);
+                goto out;
+        }
+
+        new->dev = old->dev;
+        new->ino = old->ino;
+        get_inotify_watch(&old->parent->wdata);
+        new->parent = old->parent;
+
+out:
+        return new;
+}
+
+static void audit_watch_log_rule_change(struct audit_krule *r, struct audit_watch *w, char *op)
+{
+        if (audit_enabled) {
+                struct audit_buffer *ab;
+                ab = audit_log_start(NULL, GFP_NOFS, AUDIT_CONFIG_CHANGE);
+                audit_log_format(ab, "auid=%u ses=%u op=",
+                                 audit_get_loginuid(current),
+                                 audit_get_sessionid(current));
+                audit_log_string(ab, op);
+                audit_log_format(ab, " path=");
+                audit_log_untrustedstring(ab, w->path);
+                if (r->filterkey) {
+                        audit_log_format(ab, " key=");
+                        audit_log_untrustedstring(ab, r->filterkey);
+                } else
+                        audit_log_format(ab, " key=(null)");
+                audit_log_format(ab, " list=%d res=1", r->listnr);
+                audit_log_end(ab);
+        }
+}
+
+/* Update inode info in audit rules based on filesystem event. */
+static void audit_update_watch(struct audit_parent *parent,
+                               const char *dname, dev_t dev,
+                               unsigned long ino, unsigned invalidating)
+{
+        struct audit_watch *owatch, *nwatch, *nextw;
+        struct audit_krule *r, *nextr;
+        struct audit_entry *oentry, *nentry;
+
+        mutex_lock(&audit_filter_mutex);
+        list_for_each_entry_safe(owatch, nextw, &parent->watches, wlist) {
+                if (audit_compare_dname_path(dname, owatch->path, NULL))
+                        continue;
+
+                /* If the update involves invalidating rules, do the inode-based
+                 * filtering now, so we don't omit records. */
+                if (invalidating && current->audit_context)
+                        audit_filter_inodes(current, current->audit_context);
+
+                nwatch = audit_dupe_watch(owatch);
+                if (IS_ERR(nwatch)) {
+                        mutex_unlock(&audit_filter_mutex);
+                        audit_panic("error updating watch, skipping");
+                        return;
+                }
+                nwatch->dev = dev;
+                nwatch->ino = ino;
+
+                list_for_each_entry_safe(r, nextr, &owatch->rules, rlist) {
+
+                        oentry = container_of(r, struct audit_entry, rule);
+                        list_del(&oentry->rule.rlist);
+                        list_del_rcu(&oentry->list);
+
+                        nentry = audit_dupe_rule(&oentry->rule, nwatch);
+                        if (IS_ERR(nentry)) {
+                                list_del(&oentry->rule.list);
+                                audit_panic("error updating watch, removing");
+                        } else {
+                                int h = audit_hash_ino((u32)ino);
+                                list_add(&nentry->rule.rlist, &nwatch->rules);
+                                list_add_rcu(&nentry->list, &audit_inode_hash[h]);
+                                list_replace(&oentry->rule.list,
+                                             &nentry->rule.list);
+                        }
+
+                        audit_watch_log_rule_change(r, owatch, "updated rules");
+
+                        call_rcu(&oentry->rcu, audit_free_rule_rcu);
+                }
+
+                audit_remove_watch(owatch);
+                goto add_watch_to_parent; /* event applies to a single watch */
+        }
+        mutex_unlock(&audit_filter_mutex);
+        return;
+
+add_watch_to_parent:
+        list_add(&nwatch->wlist, &parent->watches);
+        mutex_unlock(&audit_filter_mutex);
+        return;
+}
+
+/* Remove all watches & rules associated with a parent that is going away. */
+static void audit_remove_parent_watches(struct audit_parent *parent)
+{
+        struct audit_watch *w, *nextw;
+        struct audit_krule *r, *nextr;
+        struct audit_entry *e;
+
+        mutex_lock(&audit_filter_mutex);
+        parent->flags |= AUDIT_PARENT_INVALID;
+        list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
+                list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
+                        e = container_of(r, struct audit_entry, rule);
+                        audit_watch_log_rule_change(r, w, "remove rule");
+                        list_del(&r->rlist);
+                        list_del(&r->list);
+                        list_del_rcu(&e->list);
+                        call_rcu(&e->rcu, audit_free_rule_rcu);
+                }
+                audit_remove_watch(w);
+        }
+        mutex_unlock(&audit_filter_mutex);
+}
+
+/* Unregister inotify watches for parents on in_list.
+ * Generates an IN_IGNORED event. */
+void audit_inotify_unregister(struct list_head *in_list)
+{
+        struct audit_parent *p, *n;
+
+        list_for_each_entry_safe(p, n, in_list, ilist) {
+                list_del(&p->ilist);
+                inotify_rm_watch(audit_ih, &p->wdata);
+                /* the unpin matching the pin in audit_do_del_rule() */
+                unpin_inotify_watch(&p->wdata);
+        }
+}
+
+/* Get path information necessary for adding watches. */
+int audit_get_nd(char *path, struct nameidata **ndp, struct nameidata **ndw)
+{
+        struct nameidata *ndparent, *ndwatch;
+        int err;
+
+        ndparent = kmalloc(sizeof(*ndparent), GFP_KERNEL);
+        if (unlikely(!ndparent))
+                return -ENOMEM;
+
+        ndwatch = kmalloc(sizeof(*ndwatch), GFP_KERNEL);
+        if (unlikely(!ndwatch)) {
+                kfree(ndparent);
+                return -ENOMEM;
+        }
+
+        err = path_lookup(path, LOOKUP_PARENT, ndparent);
+        if (err) {
+                kfree(ndparent);
+                kfree(ndwatch);
+                return err;
+        }
+
+        err = path_lookup(path, 0, ndwatch);
+        if (err) {
+                kfree(ndwatch);
+                ndwatch = NULL;
+        }
+
+        *ndp = ndparent;
+        *ndw = ndwatch;
+
+        return 0;
+}
+
+/* Release resources used for watch path information. */
+void audit_put_nd(struct nameidata *ndp, struct nameidata *ndw)
+{
+        if (ndp) {
+                path_put(&ndp->path);
+                kfree(ndp);
+        }
+        if (ndw) {
+                path_put(&ndw->path);
+                kfree(ndw);
+        }
+}
+
+/* Associate the given rule with an existing parent inotify_watch.
+ * Caller must hold audit_filter_mutex. */
+static void audit_add_to_parent(struct audit_krule *krule,
+                                struct audit_parent *parent)
+{
+        struct audit_watch *w, *watch = krule->watch;
+        int watch_found = 0;
+
+        list_for_each_entry(w, &parent->watches, wlist) {
+                if (strcmp(watch->path, w->path))
+                        continue;
+
+                watch_found = 1;
+
+                /* put krule's and initial refs to temporary watch */
+                audit_put_watch(watch);
+                audit_put_watch(watch);
+
+                audit_get_watch(w);
+                krule->watch = watch = w;
+                break;
+        }
+
+        if (!watch_found) {
+                get_inotify_watch(&parent->wdata);
+                watch->parent = parent;
+
+                list_add(&watch->wlist, &parent->watches);
+        }
+        list_add(&krule->rlist, &watch->rules);
+}
+
+/* Find a matching watch entry, or add this one.
+ * Caller must hold audit_filter_mutex. */
+int audit_add_watch(struct audit_krule *krule, struct nameidata *ndp,
+                    struct nameidata *ndw)
+{
+        struct audit_watch *watch = krule->watch;
+        struct inotify_watch *i_watch;
+        struct audit_parent *parent;
+        int ret = 0;
+
+        /* update watch filter fields */
+        if (ndw) {
+                watch->dev = ndw->path.dentry->d_inode->i_sb->s_dev;
+                watch->ino = ndw->path.dentry->d_inode->i_ino;
+        }
+
+        /* The audit_filter_mutex must not be held during inotify calls because
+         * we hold it during inotify event callback processing.  If an existing
+         * inotify watch is found, inotify_find_watch() grabs a reference before
+         * returning.
+         */
+        mutex_unlock(&audit_filter_mutex);
+
+        if (inotify_find_watch(audit_ih, ndp->path.dentry->d_inode,
+                               &i_watch) < 0) {
+                parent = audit_init_parent(ndp);
+                if (IS_ERR(parent)) {
+                        /* caller expects mutex locked */
+                        mutex_lock(&audit_filter_mutex);
+                        return PTR_ERR(parent);
+                }
+        } else
+                parent = container_of(i_watch, struct audit_parent, wdata);
+
+        mutex_lock(&audit_filter_mutex);
+
+        /* parent was moved before we took audit_filter_mutex */
+        if (parent->flags & AUDIT_PARENT_INVALID)
+                ret = -ENOENT;
+        else
+                audit_add_to_parent(krule, parent);
+
+        /* match get in audit_init_parent or inotify_find_watch */
+        put_inotify_watch(&parent->wdata);
+        return ret;
+}
+
+void audit_remove_watch_rule(struct audit_krule *krule, struct list_head *list)
+{
+        struct audit_watch *watch = krule->watch;
+        struct audit_parent *parent = watch->parent;
+
+        list_del(&krule->rlist);
+
+        if (list_empty(&watch->rules)) {
+                audit_remove_watch(watch);
+
+                if (list_empty(&parent->watches)) {
+                        /* Put parent on the inotify un-registration
+                         * list.  Grab a reference before releasing
+                         * audit_filter_mutex, to be released in
+                         * audit_inotify_unregister().
+                         * If filesystem is going away, just leave
+                         * the sucker alone, eviction will take
+                         * care of it. */
+                        if (pin_inotify_watch(&parent->wdata))
+                                list_add(&parent->ilist, list);
+                }
+        }
+}
+
+/* Update watch data in audit rules based on inotify events. */
+static void audit_handle_ievent(struct inotify_watch *i_watch, u32 wd, u32 mask,
+                         u32 cookie, const char *dname, struct inode *inode)
+{
+        struct audit_parent *parent;
+
+        parent = container_of(i_watch, struct audit_parent, wdata);
+
+        if (mask & (IN_CREATE|IN_MOVED_TO) && inode)
+                audit_update_watch(parent, dname, inode->i_sb->s_dev,
+                                   inode->i_ino, 0);
+        else if (mask & (IN_DELETE|IN_MOVED_FROM))
+                audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
+        /* inotify automatically removes the watch and sends IN_IGNORED */
+        else if (mask & (IN_DELETE_SELF|IN_UNMOUNT))
+                audit_remove_parent_watches(parent);
+        /* inotify does not remove the watch, so remove it manually */
+        else if(mask & IN_MOVE_SELF) {
+                audit_remove_parent_watches(parent);
+                inotify_remove_watch_locked(audit_ih, i_watch);
+        } else if (mask & IN_IGNORED)
+                put_inotify_watch(i_watch);
+}
+
+static const struct inotify_operations audit_inotify_ops = {
+        .handle_event   = audit_handle_ievent,
+        .destroy_watch  = audit_free_parent,
+};
+
+static int __init audit_watch_init(void)
+{
+        audit_ih = inotify_init(&audit_inotify_ops);
+        if (IS_ERR(audit_ih))
+                audit_panic("cannot initialize inotify handle");
+        return 0;
+}
+subsys_initcall(audit_watch_init);