[PATCH 6.18 237/396] mm: memcg: initialize *locked in memcg1_oom_prepare() stub

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Breno Leitao <[email protected]>

commit 1833ce36b35426504c64600c94f322437ea44bb2 upstream.

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/[email protected]
Fixes: e93d4166b40a ("mm: memcg: put cgroup v1-specific code under a config option")
Signed-off-by: Breno Leitao <[email protected]>
Reviewed-by: Joshua Hahn <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Reviewed-by: SeongJae Park <[email protected]>
Acked-by: Shakeel Butt <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 mm/memcontrol-v1.h |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/mm/memcontrol-v1.h
+++ b/mm/memcontrol-v1.h
@@ -103,7 +103,11 @@ static inline void memcg1_remove_from_tr
 static inline void memcg1_soft_limit_reset(struct mem_cgroup *memcg) {}
 static inline void memcg1_css_offline(struct mem_cgroup *memcg) {}
 
-static inline bool memcg1_oom_prepare(struct mem_cgroup *memcg, bool *locked) { return true; }
+static inline bool memcg1_oom_prepare(struct mem_cgroup *memcg, bool *locked)
+{
+	*locked = false;
+	return true;
+}
 static inline void memcg1_oom_finish(struct mem_cgroup *memcg, bool locked) {}
 static inline void memcg1_oom_recover(struct mem_cgroup *memcg) {}