1 files changed, 255 insertions, 0 deletions
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
new file mode 100644
index 000000000000..bbcfccd4a8ea
--- /dev/null
+++ b/fs/notify/fanotify/fanotify.c
@@ -0,0 +1,255 @@
+#include <linux/fanotify.h>
+#include <linux/fdtable.h>
+#include <linux/fsnotify_backend.h>
+#include <linux/init.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h> /* UINT_MAX */
+#include <linux/mount.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <linux/wait.h>
+
+static bool should_merge(struct fsnotify_event *old, struct fsnotify_event *new)
+{
+	pr_debug("%s: old=%p new=%p\n", __func__, old, new);
+
+	if (old->to_tell == new->to_tell &&
+	    old->data_type == new->data_type &&
+	    old->tgid == new->tgid) {
+		switch (old->data_type) {
+		case (FSNOTIFY_EVENT_PATH):
+			if ((old->path.mnt == new->path.mnt) &&
+			    (old->path.dentry == new->path.dentry))
+				return true;
+		case (FSNOTIFY_EVENT_NONE):
+			return true;
+		default:
+			BUG();
+		};
+	}
+	return false;
+}
+
+/* Note, if we return an event in *arg that a reference is being held... */
+static int fanotify_merge(struct list_head *list,
+			  struct fsnotify_event *event,
+			  void **arg)
+{
+	struct fsnotify_event_holder *test_holder;
+	struct fsnotify_event *test_event;
+	struct fsnotify_event *new_event;
+	struct fsnotify_event **return_event = (struct fsnotify_event **)arg;
+	int ret = 0;
+
+	pr_debug("%s: list=%p event=%p\n", __func__, list, event);
+
+	*return_event = NULL;
+
+	/* and the list better be locked by something too! */
+
+	list_for_each_entry_reverse(test_holder, list, event_list) {
+		test_event = test_holder->event;
+		if (should_merge(test_event, event)) {
+			fsnotify_get_event(test_event);
+			*return_event = test_event;
+
+			ret = -EEXIST;
+			/* if they are exactly the same we are done */
+			if (test_event->mask == event->mask)
+				goto out;
+
+			/*
+			 * if the refcnt == 1 this is the only queue
+			 * for this event and so we can update the mask
+			 * in place.
+			 */
+			if (atomic_read(&test_event->refcnt) == 1) {
+				test_event->mask |= event->mask;
+				goto out;
+			}
+
+			/* can't allocate memory, merge was no possible */
+			new_event = fsnotify_clone_event(test_event);
+			if (unlikely(!new_event)) {
+				ret = 0;
+				goto out;
+			}
+
+			/* we didn't return the test_event, so drop that ref */
+			fsnotify_put_event(test_event);
+			/* the reference we return on new_event is from clone */
+			*return_event = new_event;
+
+			/* build new event and replace it on the list */
+			new_event->mask = (test_event->mask | event->mask);
+			fsnotify_replace_event(test_holder, new_event);
+
+			break;
+		}
+	}
+out:
+	return ret;
+}
+
+#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
+static int fanotify_get_response_from_access(struct fsnotify_group *group,
+					     struct fsnotify_event *event)
+{
+	int ret;
+
+	pr_debug("%s: group=%p event=%p\n", __func__, group, event);
+
+	wait_event(group->fanotify_data.access_waitq, event->response);
+
+	/* userspace responded, convert to something usable */
+	spin_lock(&event->lock);
+	switch (event->response) {
+	case FAN_ALLOW:
+		ret = 0;
+		break;
+	case FAN_DENY:
+	default:
+		ret = -EPERM;
+	}
+	event->response = 0;
+	spin_unlock(&event->lock);
+
+	pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
+		 group, event, ret);
+	
+	return ret;
+}
+#endif
+
+static int fanotify_handle_event(struct fsnotify_group *group, struct fsnotify_event *event)
+{
+	int ret;
+	struct fsnotify_event *notify_event = NULL;
+
+	BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
+	BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
+	BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
+	BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
+	BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
+	BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
+	BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
+	BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
+	BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
+
+	pr_debug("%s: group=%p event=%p\n", __func__, group, event);
+
+	ret = fsnotify_add_notify_event(group, event, NULL, fanotify_merge,
+					(void **)&notify_event);
+	/* -EEXIST means this event was merged with another, not that it was an error */
+	if (ret == -EEXIST)
+		ret = 0;
+	if (ret)
+		goto out;
+
+#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
+	if (event->mask & FAN_ALL_PERM_EVENTS) {
+		/* if we merged we need to wait on the new event */
+		if (notify_event)
+			event = notify_event;
+		ret = fanotify_get_response_from_access(group, event);
+	}
+#endif
+
+out:
+	if (notify_event)
+		fsnotify_put_event(notify_event);
+	return ret;
+}
+
+static bool should_send_vfsmount_event(struct fsnotify_group *group, struct vfsmount *mnt,
+				       struct inode *inode, __u32 mask)
+{
+	struct fsnotify_mark *mnt_mark;
+	struct fsnotify_mark *inode_mark;
+
+	pr_debug("%s: group=%p vfsmount=%p mask=%x\n",
+		 __func__, group, mnt, mask);
+
+	mnt_mark = fsnotify_find_vfsmount_mark(group, mnt);
+	if (!mnt_mark)
+		return false;
+
+	mask &= mnt_mark->mask;
+	mask &= ~mnt_mark->ignored_mask;
+
+	if (mask) {
+		inode_mark = fsnotify_find_inode_mark(group, inode);
+		if (inode_mark) {
+			mask &= ~inode_mark->ignored_mask;
+			fsnotify_put_mark(inode_mark);
+		}
+	}
+
+	/* find took a reference */
+	fsnotify_put_mark(mnt_mark);
+
+	return mask;
+}
+
+static bool should_send_inode_event(struct fsnotify_group *group, struct inode *inode,
+				    __u32 mask)
+{
+	struct fsnotify_mark *fsn_mark;
+
+	pr_debug("%s: group=%p inode=%p mask=%x\n",
+		 __func__, group, inode, mask);
+
+	fsn_mark = fsnotify_find_inode_mark(group, inode);
+	if (!fsn_mark)
+		return false;
+
+	/* if the event is for a child and this inode doesn't care about
+	 * events on the child, don't send it! */
+	if ((mask & FS_EVENT_ON_CHILD) &&
+	    !(fsn_mark->mask & FS_EVENT_ON_CHILD)) {
+		mask = 0;
+	} else {
+		/*
+		 * We care about children, but do we care about this particular
+		 * type of event?
+		 */
+		mask &= ~FS_EVENT_ON_CHILD;
+		mask &= fsn_mark->mask;
+		mask &= ~fsn_mark->ignored_mask;
+	}
+
+	/* find took a reference */
+	fsnotify_put_mark(fsn_mark);
+
+	return mask;
+}
+
+static bool fanotify_should_send_event(struct fsnotify_group *group, struct inode *to_tell,
+				       struct vfsmount *mnt, __u32 mask, void *data,
+				       int data_type)
+{
+	pr_debug("%s: group=%p to_tell=%p mnt=%p mask=%x data=%p data_type=%d\n",
+		 __func__, group, to_tell, mnt, mask, data, data_type);
+
+	/* sorry, fanotify only gives a damn about files and dirs */
+	if (!S_ISREG(to_tell->i_mode) &&
+	    !S_ISDIR(to_tell->i_mode))
+		return false;
+
+	/* if we don't have enough info to send an event to userspace say no */
+	if (data_type != FSNOTIFY_EVENT_PATH)
+		return false;
+
+	if (mnt)
+		return should_send_vfsmount_event(group, mnt, to_tell, mask);
+	else
+		return should_send_inode_event(group, to_tell, mask);
+}
+
+const struct fsnotify_ops fanotify_fsnotify_ops = {
+	.handle_event = fanotify_handle_event,
+	.should_send_event = fanotify_should_send_event,
+	.free_group_priv = NULL,
+	.free_event_priv = NULL,
+	.freeing_mark = NULL,
+};