fanotify: groups can specify their f_flags for new fd

Currently fanotify fds opened for thier listeners are done with f_flags
equal to O_RDONLY | O_LARGEFILE.  This patch instead takes f_flags from the
fanotify_init syscall and uses those when opening files in the context of
the listener.
Signed-off-by: NEric Paris <eparis@redhat.com>

fs/notify/fanotify/fanotify_user.c

@@ -81,7 +81,7 @@ static int create_fd(struct fsnotify_group *group, struct fsnotify_event *event)
 	 * are NULL;  That's fine, just don't call dentry open */
 	if (dentry && mnt)
 		new_file = dentry_open(dentry, mnt,
-				       O_RDONLY | O_LARGEFILE | FMODE_NONOTIFY,
+				       group->fanotify_data.f_flags | FMODE_NONOTIFY,
 				       current_cred());
 	else
 		new_file = ERR_PTR(-EOVERFLOW);
@@ -625,9 +625,6 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 	pr_debug("%s: flags=%d event_f_flags=%d\n",
 		__func__, flags, event_f_flags);
 
-	if (event_f_flags)
-		return -EINVAL;
-
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;
 
@@ -645,6 +642,7 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 	if (IS_ERR(group))
 		return PTR_ERR(group);
 
+	group->fanotify_data.f_flags = event_f_flags;
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 	mutex_init(&group->fanotify_data.access_mutex);
 	init_waitqueue_head(&group->fanotify_data.access_waitq);

include/linux/fsnotify_backend.h

@@ -169,14 +169,17 @@ struct fsnotify_group {
 			struct user_struct      *user;
 		} inotify_data;
 #endif
-#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
+#ifdef CONFIG_FANOTIFY
 		struct fanotify_group_private_data {
+#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 			/* allows a group to block waiting for a userspace response */
 			struct mutex access_mutex;
 			struct list_head access_list;
 			wait_queue_head_t access_waitq;
+#endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
+			int f_flags;
 		} fanotify_data;
-#endif
+#endif /* CONFIG_FANOTIFY */
 	};
 };