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Breno Leitao
1833ce36b3
mem_cgroup_oom() passes an uninitialized "locked" to memcg1_oom_prepare()
and reads it back in memcg1_oom_finish():
bool locked, ret;
...
if (!memcg1_oom_prepare(memcg, &locked))
return false;
ret = mem_cgroup_out_of_memory(memcg, mask, order);
memcg1_oom_finish(memcg, locked);
This relies on memcg1_oom_prepare() setting *locked whenever it returns
true. The CONFIG_MEMCG_V1=y version does, but the stub used when
CONFIG_MEMCG_V1=n returns true without touching *locked, so
memcg1_oom_finish() consumes an uninitialized value. On a memcg OOM this
is reported by UBSAN:
UBSAN: invalid-load in mm/memcontrol.c:1932:27
load of value 0 is not a valid value for type 'bool' (aka '_Bool')
Initialize *locked to false in the stub; with cgroup v1 compiled out there
is no OOM lock to take.
Link: https://lore.kernel.org/20260716-memcg-oom-uninit-locked-v2-1-63631d878eb4@debian.org
Fixes: e93d4166b4 ("mm: memcg: put cgroup v1-specific code under a config option")
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Joshua Hahn <joshua.hahnjy@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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