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Subject[PATCH] memcg: do not expose uninitialized mem_cgroup_per_node to world
Date
Freshly allocated 'mem_cgroup_per_node' list entries must be
initialized before the rest of the kernel can see them. Otherwise
zero initialized list fields can lead to race condition at
mem_cgroup_force_empty_list:
pc = list_entry(list->prev, struct page_cgroup, lru);
where 'pc' will be something like 0xfffffffc if list->prev is 0
and cause page fault later when 'pc' is dereferenced.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
mm/memcontrol.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index bd9052a..ee7cb4c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4707,7 +4707,6 @@ static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
if (!pn)
return 1;

- mem->info.nodeinfo[node] = pn;
for (zone = 0; zone < MAX_NR_ZONES; zone++) {
mz = &pn->zoneinfo[zone];
for_each_lru(l)
@@ -4716,6 +4715,7 @@ static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
mz->on_tree = false;
mz->mem = mem;
}
+ mem->info.nodeinfo[node] = pn;
return 0;
}

--
1.7.1


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