fanotify: userspace interface for permission responses
fanotify groups need to respond to events which include permissions types.
To do so groups will send a response using write() on the fanotify_fd they
have open.
Signed-off-by: Eric Paris <eparis@redhat.com>
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 09d9bdb..87f0be8 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -18,6 +18,13 @@
extern const struct fsnotify_ops fanotify_fsnotify_ops;
static struct kmem_cache *fanotify_mark_cache __read_mostly;
+static struct kmem_cache *fanotify_response_event_cache __read_mostly;
+
+struct fanotify_response_event {
+ struct list_head list;
+ __s32 fd;
+ struct fsnotify_event *event;
+};
/*
* Get an fsnotify notification event if one exists and is small
@@ -110,23 +117,152 @@
return metadata->fd;
}
+#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
+static struct fanotify_response_event *dequeue_re(struct fsnotify_group *group,
+ __s32 fd)
+{
+ struct fanotify_response_event *re, *return_re = NULL;
+
+ mutex_lock(&group->fanotify_data.access_mutex);
+ list_for_each_entry(re, &group->fanotify_data.access_list, list) {
+ if (re->fd != fd)
+ continue;
+
+ list_del_init(&re->list);
+ return_re = re;
+ break;
+ }
+ mutex_unlock(&group->fanotify_data.access_mutex);
+
+ pr_debug("%s: found return_re=%p\n", __func__, return_re);
+
+ return return_re;
+}
+
+static int process_access_response(struct fsnotify_group *group,
+ struct fanotify_response *response_struct)
+{
+ struct fanotify_response_event *re;
+ __s32 fd = response_struct->fd;
+ __u32 response = response_struct->response;
+
+ pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
+ fd, response);
+ /*
+ * make sure the response is valid, if invalid we do nothing and either
+ * userspace can send a valid responce or we will clean it up after the
+ * timeout
+ */
+ switch (response) {
+ case FAN_ALLOW:
+ case FAN_DENY:
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ if (fd < 0)
+ return -EINVAL;
+
+ re = dequeue_re(group, fd);
+ if (!re)
+ return -ENOENT;
+
+ re->event->response = response;
+
+ wake_up(&group->fanotify_data.access_waitq);
+
+ kmem_cache_free(fanotify_response_event_cache, re);
+
+ return 0;
+}
+
+static int prepare_for_access_response(struct fsnotify_group *group,
+ struct fsnotify_event *event,
+ __s32 fd)
+{
+ struct fanotify_response_event *re;
+
+ if (!(event->mask & FAN_ALL_PERM_EVENTS))
+ return 0;
+
+ re = kmem_cache_alloc(fanotify_response_event_cache, GFP_KERNEL);
+ if (!re)
+ return -ENOMEM;
+
+ re->event = event;
+ re->fd = fd;
+
+ mutex_lock(&group->fanotify_data.access_mutex);
+ list_add_tail(&re->list, &group->fanotify_data.access_list);
+ mutex_unlock(&group->fanotify_data.access_mutex);
+
+ return 0;
+}
+
+static void remove_access_response(struct fsnotify_group *group,
+ struct fsnotify_event *event,
+ __s32 fd)
+{
+ struct fanotify_response_event *re;
+
+ if (!(event->mask & FAN_ALL_PERM_EVENTS))
+ return;
+
+ re = dequeue_re(group, fd);
+ if (!re)
+ return;
+
+ BUG_ON(re->event != event);
+
+ kmem_cache_free(fanotify_response_event_cache, re);
+
+ return;
+}
+#else
+static int prepare_for_access_response(struct fsnotify_group *group,
+ struct fsnotify_event *event,
+ __s32 fd)
+{
+ return 0;
+}
+
+static void remove_access_response(struct fsnotify_group *group,
+ struct fsnotify_event *event,
+ __s32 fd)
+{
+ return 0;
+}
+#endif
+
static ssize_t copy_event_to_user(struct fsnotify_group *group,
struct fsnotify_event *event,
char __user *buf)
{
struct fanotify_event_metadata fanotify_event_metadata;
- int ret;
+ int fd, ret;
pr_debug("%s: group=%p event=%p\n", __func__, group, event);
- ret = fill_event_metadata(group, &fanotify_event_metadata, event);
- if (ret < 0)
- return ret;
+ fd = fill_event_metadata(group, &fanotify_event_metadata, event);
+ if (fd < 0)
+ return fd;
+ ret = prepare_for_access_response(group, event, fd);
+ if (ret)
+ goto out_close_fd;
+
+ ret = -EFAULT;
if (copy_to_user(buf, &fanotify_event_metadata, FAN_EVENT_METADATA_LEN))
- return -EFAULT;
+ goto out_kill_access_response;
return FAN_EVENT_METADATA_LEN;
+
+out_kill_access_response:
+ remove_access_response(group, event, fd);
+out_close_fd:
+ sys_close(fd);
+ return ret;
}
/* intofiy userspace file descriptor functions */
@@ -197,6 +333,33 @@
return ret;
}
+static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
+{
+#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
+ struct fanotify_response response = { .fd = -1, .response = -1 };
+ struct fsnotify_group *group;
+ int ret;
+
+ group = file->private_data;
+
+ if (count > sizeof(response))
+ count = sizeof(response);
+
+ pr_debug("%s: group=%p count=%zu\n", __func__, group, count);
+
+ if (copy_from_user(&response, buf, count))
+ return -EFAULT;
+
+ ret = process_access_response(group, &response);
+ if (ret < 0)
+ count = ret;
+
+ return count;
+#else
+ return -EINVAL;
+#endif
+}
+
static int fanotify_release(struct inode *ignored, struct file *file)
{
struct fsnotify_group *group = file->private_data;
@@ -237,6 +400,7 @@
static const struct file_operations fanotify_fops = {
.poll = fanotify_poll,
.read = fanotify_read,
+ .write = fanotify_write,
.fasync = NULL,
.release = fanotify_release,
.unlocked_ioctl = fanotify_ioctl,
@@ -470,7 +634,7 @@
if (flags & ~FAN_ALL_INIT_FLAGS)
return -EINVAL;
- f_flags = (O_RDONLY | FMODE_NONOTIFY);
+ f_flags = O_RDWR | FMODE_NONOTIFY;
if (flags & FAN_CLOEXEC)
f_flags |= O_CLOEXEC;
if (flags & FAN_NONBLOCK)
@@ -527,7 +691,11 @@
default:
return -EINVAL;
}
+#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
+ if (mask & ~(FAN_ALL_EVENTS | FAN_ALL_PERM_EVENTS | FAN_EVENT_ON_CHILD))
+#else
if (mask & ~(FAN_ALL_EVENTS | FAN_EVENT_ON_CHILD))
+#endif
return -EINVAL;
filp = fget_light(fanotify_fd, &fput_needed);
@@ -600,6 +768,8 @@
static int __init fanotify_user_setup(void)
{
fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, SLAB_PANIC);
+ fanotify_response_event_cache = KMEM_CACHE(fanotify_response_event,
+ SLAB_PANIC);
return 0;
}