fuse_dev_ioctl() performed fuse_get_dev() on a user-supplied fd,
leading to a type confusion issue. Fix it by checking file->f_op.
Signed-off-by: NJann Horn <jann@thejh.net>
Acked-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>