Re: [PATCH] mm/memcontrol: fix data-race on reading jiffies_64

[Muchun Song]

> On Aug 27, 2026, at 10:54, Jiayuan Chen <jiayuan.chen@xxxxxxxxx> wrote:
> 
> KCSAN reported a data-race between tick_do_update_jiffies64() updating
> jiffies_64 and mem_cgroup_flush_stats_ratelimited() reading it directly.
> 
> Unlike jiffies, jiffies_64 is not volatile, so raw reads are plain
> accesses and can even be torn on 32-bit. Use get_jiffies_64() instead,
> and fix the same pattern in mem_cgroup_flush_foreign().
> 
> Cc: <stable@xxxxxxxxxxxxxxx>
> Fixes: 508bed884767 ("mm: memcg: change flush_next_time to flush_last_time")
> Fixes: 97b27821b485 ("writeback, memcg: Implement foreign dirty flushing")
> Reported-by: syzbot+ced4d9a8cadb5ef3adae@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Jiayuan Chen <jiayuan.chen@xxxxxxxxx>

Acked-by: Muchun Song <muchun.song@xxxxxxxxx>

Thanks.