lkml.org 
[lkml]   [2015]   [Sep]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [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?




\
 
 \ /
  Last update: 2015-09-30 01:21    [W:0.085 / U:0.320 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site