Messages in this thread | | | From | Shakeel Butt <> | Date | Thu, 29 Oct 2020 08:52:03 -0700 | Subject | Re: [PATCH v2] mm: memcg/slab: Fix use after free in obj_cgroup_charge |
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On Tue, Oct 27, 2020 at 8:51 PM Muchun Song <songmuchun@bytedance.com> wrote: > > The rcu_read_lock/unlock only can guarantee that the memcg will > not be freed, but it cannot guarantee the success of css_get to > memcg. > > If the whole process of a cgroup offlining is completed between > reading a objcg->memcg pointer and bumping the css reference on > another CPU, and there are exactly 0 external references to this > memory cgroup (how we get to the obj_cgroup_charge() then?), > css_get() can change the ref counter from 0 back to 1. > > Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API") > Signed-off-by: Muchun Song <songmuchun@bytedance.com> > Acked-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
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