Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1233187 > unrolled thread

[PATCH 2/5] fs: charge pipe buffers to memcg

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  [PATCH 2/5] fs: charge pipe buffers to memcg Vladimir Davydov <vdavydov@parallels.com> - 2015-09-26 12:50 +0200
    Re: [PATCH 2/5] fs: charge pipe buffers to memcg Andrew Morton <akpm@linux-foundation.org> - 2015-09-30 01:00 +0200
      Re: [PATCH 2/5] fs: charge pipe buffers to memcg Vladimir Davydov <vdavydov@virtuozzo.com> - 2015-09-30 19:00 +0200

#1233187 — [PATCH 2/5] fs: charge pipe buffers to memcg

Pipe buffers can be generated unrestrictedly by an unprivileged
userspace process, so they shouldn't go unaccounted.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
---
 fs/pipe.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/pipe.c b/fs/pipe.c
index 8865f7963700..6880884b70b0 100644
--- 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;
-- 
2.1.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [next] | [standalone]

#1235623

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?


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [prev] | [next] | [standalone]

#1236543

On Tue, Sep 29, 2015 at 03:57:11PM -0700, Andrew Morton wrote:
> 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?

Right you are! I completely forgot of vmsplice case. Surely, we need to
uncharge the page in the ->steal method and clear its PageKmem. Will fix
that.

Thanks,
Vladimir
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web