On 13.09.2016 22:15, Jan Kara wrote:
> Fanotify code has an own lock (access_lock) to protect a list of events
> waiting for a response from userspace. However this is somewhat awkward
> as the same list_head in the event is protected by notification_lock
> if it is part of the notification queue and by access_lock if it is part
> of the fanotify private queue which makes it difficult for any reliable
> checks in the generic code. So make fanotify use the same lock -
> notification_lock - for protecting its private event list.
>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> fs/notify/fanotify/fanotify_user.c | 13 +++++--------
> include/linux/fsnotify_backend.h | 1 -
> 2 files changed, 5 insertions(+), 9 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index e6f3fe9bb2ed..aed06fe2533d 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -147,7 +147,7 @@ static struct fanotify_perm_event_info *dequeue_event(
> {
> struct fanotify_perm_event_info *event, *return_e = NULL;
>
> - spin_lock(&group->fanotify_data.access_lock);
> + spin_lock(&group->notification_lock);
> list_for_each_entry(event, &group->fanotify_data.access_list,
> fae.fse.list) {
> if (event->fd != fd)
> @@ -157,7 +157,7 @@ static struct fanotify_perm_event_info *dequeue_event(
> return_e = event;
> break;
> }
> - spin_unlock(&group->fanotify_data.access_lock);
> + spin_unlock(&group->notification_lock);
>
> pr_debug("%s: found return_re=%p\n", __func__, return_e);
>
> @@ -309,10 +309,10 @@ static ssize_t fanotify_read(struct file *file, char __user *buf,
> wake_up(&group->fanotify_data.access_waitq);
> break;
> }
> - spin_lock(&group->fanotify_data.access_lock);
> + spin_lock(&group->notification_lock);
> list_add_tail(&kevent->list,
> &group->fanotify_data.access_list);
> - spin_unlock(&group->fanotify_data.access_lock);
> + spin_unlock(&group->notification_lock);
> #endif
> }
> buf += ret;
> @@ -371,7 +371,7 @@ static int fanotify_release(struct inode *ignored, struct file *file)
> * Process all permission events on access_list and notification queue
> * and simulate reply from userspace.
> */
> - spin_lock(&group->fanotify_data.access_lock);
> + spin_lock(&group->notification_lock);
> list_for_each_entry_safe(event, next, &group->fanotify_data.access_list,
> fae.fse.list) {
> pr_debug("%s: found group=%p event=%p\n", __func__, group,
> @@ -380,14 +380,12 @@ static int fanotify_release(struct inode *ignored, struct file *file)
> list_del_init(&event->fae.fse.list);
> event->response = FAN_ALLOW;
> }
> - spin_unlock(&group->fanotify_data.access_lock);
>
> /*
> * Destroy all non-permission events. For permission events just
> * dequeue them and set the response. They will be freed once the
> * response is consumed and fanotify_get_response() returns.
> */
> - spin_lock(&group->notification_lock);
> while (!fsnotify_notify_queue_is_empty(group)) {
> fsn_event = fsnotify_remove_first_event(group);
> if (!(fsn_event->mask & FAN_ALL_PERM_EVENTS)) {
> @@ -767,7 +765,6 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
> event_f_flags |= O_LARGEFILE;
> group->fanotify_data.f_flags = event_f_flags;
> #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
> - spin_lock_init(&group->fanotify_data.access_lock);
> init_waitqueue_head(&group->fanotify_data.access_waitq);
> INIT_LIST_HEAD(&group->fanotify_data.access_list);
> #endif
> diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
> index 0713e873b1c9..79467b239fcf 100644
> --- a/include/linux/fsnotify_backend.h
> +++ b/include/linux/fsnotify_backend.h
> @@ -177,7 +177,6 @@ struct fsnotify_group {
> struct fanotify_group_private_data {
> #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
> /* allows a group to block waiting for a userspace response */
> - spinlock_t access_lock;
> struct list_head access_list;
> wait_queue_head_t access_waitq;
> #endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
>
Reviewed-by: Lino Sanfilippo <LinoSanfilippo@xxxxxx>
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