Re: [PATCH v2 2/2] mm: memcg: use READ_ONCE()/WRITE_ONCE() to access stock->cached

[Shakeel Butt]

On Tue, May 02, 2023 at 09:08:39AM -0700, Roman Gushchin wrote:
> A memcg pointer in the percpu stock can be accessed by drain_all_stock()
> from another cpu in a lockless way.
> In theory it might lead to an issue, similar to the one which has been
> discovered with stock->cached_objcg, where the pointer was zeroed
> between the check for being NULL and dereferencing.
> In this case the issue is unlikely a real problem, but to make it
> bulletproof and similar to stock->cached_objcg, let's annotate all
> accesses to stock->cached with READ_ONCE()/WTRITE_ONCE().
> 
> Signed-off-by: Roman Gushchin <roman.gushchin@xxxxxxxxx>
> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
> Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>

Acked-by: Shakeel Butt <shakeelb@xxxxxxxxxx>