Merge tag 'fsnotify_for_v6.12-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs

Pull fsnotify fixes from Jan Kara:
 "Fixes for an inotify deadlock and a data race in fsnotify"

* tag 'fsnotify_for_v6.12-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  inotify: Fix possible deadlock in fsnotify_destroy_mark
  fsnotify: Avoid data race between fsnotify_recalc_mask() and fsnotify_object_watched()

1 files changed, 6 insertions, 2 deletions

diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 5e170e713088..c45b222cf9c1 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -128,7 +128,7 @@ __u32 fsnotify_conn_mask(struct fsnotify_mark_connector *conn)
 	if (WARN_ON(!fsnotify_valid_obj_type(conn->type)))
 		return 0;
 
-	return *fsnotify_conn_mask_p(conn);
+	return READ_ONCE(*fsnotify_conn_mask_p(conn));
 }
 
 static void fsnotify_get_sb_watched_objects(struct super_block *sb)
@@ -245,7 +245,11 @@ static void *__fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
 		    !(mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF))
 			want_iref = true;
 	}
-	*fsnotify_conn_mask_p(conn) = new_mask;
+	/*
+	 * We use WRITE_ONCE() to prevent silly compiler optimizations from
+	 * confusing readers not holding conn->lock with partial updates.
+	 */
+	WRITE_ONCE(*fsnotify_conn_mask_p(conn), new_mask);
 
 	return fsnotify_update_iref(conn, want_iref);
 }