fanotify: use notification_lock instead of access_lock

Fanotify code has its 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.

Link: http://lkml.kernel.org/r/1473797711-14111-6-git-send-email-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 80091a5..189fab3 100644 (file)
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -148,7 +148,7 @@ 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)
@@ -158,7 +158,7 @@ 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);
 
@@ -310,10 +310,10 @@ 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;
@@ -372,7 +372,7 @@ 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,
@@ -381,14 +381,12 @@ 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)) {
@@ -768,7 +766,6 @@ 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 0713e87..79467b2 100644 (file)
--- 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 */