[PATCH v2 0/4] fix unexpected type conversions and potential overflows

Qi Zheng
2026-03-25T14:13:59Z

From: Qi Zheng <zhengqi.arch@bytedance.com>

Hi all,

As Harry Yoo pointed out [1], in scenarios where massive state updates occur
(e.g., during the reparenting of LRU folios), the values passed to memcg stat
update functions can accumulate and exceed the upper limit of a 32-bit integer.

If the parameter types are not large enough (like 'int') or are handled
incorrectly, it can lead to severe truncation, potential overflow issues,
and unexpected type conversion bugs.

This series aims to address these issues by correcting the parameter types
in the relevant functions, and fixing an implicit conversion bug in
memcg_state_val_in_pages().

This series is based on the next-20260323.

Comments and suggestions are welcome!

Thanks,
Qi

[1]. https://lore.kernel.org/all/acDxaEgnqPI-Z4be@hyeyoo/

Qi Zheng (4):
mm: memcontrol: correct the type of stats_updates to unsigned long
mm: memcontrol: change val type to long in
__mod_memcg_{lruvec_}state()
mm: memcontrol: correct the nr_pages parameter type of
mem_cgroup_update_lru_size()
mm: memcontrol: fix unexpected massive positive number in
memcg_state_val_in_pages()

include/linux/memcontrol.h | 2 +-
include/trace/events/memcg.h | 10 +++++-----
mm/memcontrol.c | 37 +++++++++++++++++++-----------------
3 files changed, 26 insertions(+), 23 deletions(-)

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2.20.1