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memcg: fix per_node_info cleanup

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syzbot has triggered a NULL ptr dereference when allocation fault
injection enforces a failure and alloc_mem_cgroup_per_node_info
initializes memcg->nodeinfo only half way through.

But __mem_cgroup_free still tries to free all per-node data and
dereferences pn->lruvec_stat_cpu unconditioanlly even if the specific
per-node data hasn't been initialized.

The bug is quite unlikely to hit because small allocations do not fail
and we would need quite some numa nodes to make struct
mem_cgroup_per_node large enough to cross the costly order.

Link: http://lkml.kernel.org/r/[email protected]
Reported-by: [email protected]
Fixes: 00f3ca2c2d ("mm: memcontrol: per-lruvec stats infrastructure")
Signed-off-by: Michal Hocko <[email protected]>
Reviewed-by: Andrey Ryabinin <[email protected]>
Cc: Johannes Weiner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Michal Hocko
2018-04-11 10:28:32 -07:00
committed by Linus Torvalds
parent a06ad633a3
commit 4eaf431f6f
1 changed files with 3 additions and 0 deletions
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mm/memcontrol.c
+3
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@@ -4108,6 +4108,9 @@ static void free_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node)
{
struct mem_cgroup_per_node *pn = memcg->nodeinfo[node];
if (!pn)
return;
free_percpu(pn->lruvec_stat_cpu);
kfree(pn);
}