lkml.org 
[lkml]   [2012]   [Mar]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] page_cgroup: fix horrid swap accounting regression
On Mon 05-03-12 20:52:55, Hugh Dickins wrote:
> Why is memcg's swap accounting so broken? Insane counts, wrong ownership,
> unfreeable structures, which later get freed and then accessed after free.
>
> Turns out to be a tiny a little 3.3-rc1 regression in 9fb4b7cc0724
> "page_cgroup: add helper function to get swap_cgroup": the helper
> function (actually named lookup_swap_cgroup()) returns an address
> using void* arithmetic, but the structure in question is a short.
>
> Signed-off-by: Hugh Dickins <hughd@google.com>

Thanks, this one looks really nasty.

Acked-by: Michal Hocko <mhocko@suse.cz>

> ---
>
> mm/page_cgroup.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> --- 3.3-rc6/mm/page_cgroup.c 2012-01-20 08:42:35.320020840 -0800
> +++ linux/mm/page_cgroup.c 2012-03-05 19:51:13.535372098 -0800
> @@ -379,13 +379,15 @@ static struct swap_cgroup *lookup_swap_c
> pgoff_t offset = swp_offset(ent);
> struct swap_cgroup_ctrl *ctrl;
> struct page *mappage;
> + struct swap_cgroup *sc;
>
> ctrl = &swap_cgroup_ctrl[swp_type(ent)];
> if (ctrlp)
> *ctrlp = ctrl;
>
> mappage = ctrl->map[offset / SC_PER_PAGE];
> - return page_address(mappage) + offset % SC_PER_PAGE;
> + sc = page_address(mappage);
> + return sc + offset % SC_PER_PAGE;
> }
>
> /**

--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic


\
 
 \ /
  Last update: 2012-03-14 11:05    [W:0.066 / U:0.092 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site