Messages in this thread | | | Date | Tue, 29 Sep 2015 15:57:11 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 2/5] fs: charge pipe buffers to memcg |
| |
On Sat, 26 Sep 2015 13:45:54 +0300 Vladimir Davydov <vdavydov@parallels.com> wrote:
> Pipe buffers can be generated unrestrictedly by an unprivileged > userspace process, so they shouldn't go unaccounted. > > ... > > --- a/fs/pipe.c > +++ b/fs/pipe.c > @@ -400,7 +400,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from) > int copied; > > if (!page) { > - page = alloc_page(GFP_HIGHUSER); > + page = alloc_kmem_pages(GFP_HIGHUSER, 0); > if (unlikely(!page)) { > ret = ret ? : -ENOMEM; > break;
This seems broken. We have a page buffer page which has a weird ->mapcount. Now it gets stolen (generic_pipe_buf_steal()) and spliced into pagecache. Then the page gets mmapped and MM starts playing with its ->_mapcount?
| |