[PATCH 7/7] audit: use kern_path rather than namei for watch creation

[Eric Paris]

kernel watches jump through stupid allocation hoops to get the namei data
for the path in question and it's parent.  All useless crap since we just
need to hold a struct path for a bit.

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

 kernel/audit/audit_watch.c |   68 ++++++++++++++++----------------------------
 1 files changed, 25 insertions(+), 43 deletions(-)

diff --git a/kernel/audit/audit_watch.c b/kernel/audit/audit_watch.c
index 2ba999e..b5e369d 100644
--- a/kernel/audit/audit_watch.c
+++ b/kernel/audit/audit_watch.c
@@ -130,7 +130,7 @@ dev_t audit_watch_dev(struct audit_watch *watch)
 }
 
 /* Initialize a parent watch entry. */
-static struct audit_parent *audit_init_parent(struct nameidata *ndp)
+static struct audit_parent *audit_init_parent(struct path *parent_path)
 {
 	struct audit_parent *parent;
 	s32 wd;
@@ -146,7 +146,7 @@ static struct audit_parent *audit_init_parent(struct nameidata *ndp)
 	/* 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);
+			       parent_path->dentry->d_inode, AUDIT_IN_WATCH);
 	if (wd < 0) {
 		audit_free_parent(&parent->wdata);
 		return ERR_PTR(wd);
@@ -355,51 +355,33 @@ void audit_inotify_unregister(struct list_head *in_list)
 }
 
 /* Get path information necessary for adding watches. */
-static int audit_get_nd(char *path, struct nameidata **ndp, struct nameidata **ndw)
+static int audit_get_path(const char *path, struct path *parent_path,
+			  struct path *watch_path)
 {
-	struct nameidata *ndparent, *ndwatch;
 	int err;
 
-	ndparent = kmalloc(sizeof(*ndparent), GFP_KERNEL);
-	if (unlikely(!ndparent))
-		return -ENOMEM;
+	parent_path->dentry = NULL;
+	watch_path->dentry = NULL;
 
-	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);
+	err = kern_path(path, LOOKUP_PARENT, parent_path);
+	if (err)
 		return err;
-	}
 
-	err = path_lookup(path, 0, ndwatch);
-	if (err) {
-		kfree(ndwatch);
-		ndwatch = NULL;
-	}
-
-	*ndp = ndparent;
-	*ndw = ndwatch;
+	/* watch_path might not exist, we don't care about errors here. */
+	kern_path(path, 0, watch_path);
 
 	return 0;
 }
 
 /* Release resources used for watch path information. */
-static void audit_put_nd(struct nameidata *ndp, struct nameidata *ndw)
+static void audit_put_path(struct path *parent_path, struct path *watch_path)
 {
-	if (ndp) {
-		path_put(&ndp->path);
-		kfree(ndp);
-	}
-	if (ndw) {
-		path_put(&ndw->path);
-		kfree(ndw);
-	}
+	/* there should always be a valid parent path */
+	if (parent_path->dentry)
+		path_put(parent_path);
+	/* creating a watch on a non-existant file may not have a watch_path->dentry */
+	if (watch_path->dentry)
+		path_put(watch_path);
 }
 
 /* Associate the given rule with an existing parent inotify_watch.
@@ -441,13 +423,13 @@ int audit_add_watch(struct audit_krule *krule)
 	struct audit_watch *watch = krule->watch;
 	struct inotify_watch *i_watch;
 	struct audit_parent *parent;
-	struct nameidata *ndp = NULL, *ndw = NULL;
+	struct path parent_path, watch_path;
 	int ret = 0;
 
 	mutex_unlock(&audit_filter_mutex);
 
 	/* Avoid calling path_lookup under audit_filter_mutex. */
-	ret = audit_get_nd(watch->path, &ndp, &ndw);
+	ret = audit_get_path(watch->path, &parent_path, &watch_path);
 	if (ret) {
 		/* caller expects mutex locked */
 		mutex_lock(&audit_filter_mutex);
@@ -455,9 +437,9 @@ int audit_add_watch(struct audit_krule *krule)
 	}
 
 	/* 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;
+	if (watch_path.dentry) {
+		watch->dev = watch_path.dentry->d_inode->i_sb->s_dev;
+		watch->ino = watch_path.dentry->d_inode->i_ino;
 	}
 
 	/* The audit_filter_mutex must not be held during inotify calls because
@@ -465,9 +447,9 @@ int audit_add_watch(struct audit_krule *krule)
 	 * inotify watch is found, inotify_find_watch() grabs a reference before
 	 * returning.
 	 */
-	if (inotify_find_watch(audit_ih, ndp->path.dentry->d_inode,
+	if (inotify_find_watch(audit_ih, parent_path.dentry->d_inode,
 			       &i_watch) < 0) {
-		parent = audit_init_parent(ndp);
+		parent = audit_init_parent(&parent_path);
 		if (IS_ERR(parent)) {
 			/* caller expects mutex locked */
 			mutex_lock(&audit_filter_mutex);
@@ -489,7 +471,7 @@ int audit_add_watch(struct audit_krule *krule)
 	put_inotify_watch(&parent->wdata);
 
 error:
-	audit_put_nd(ndp, ndw);		/* NULL args OK */
+	audit_put_path(&parent_path, &watch_path);
 	return ret;
 
 }