From: Chris Down <chris@xxxxxxxxxxxxxx> Subject: mm, memcg: fix corruption on 64-bit divisor in memory.high throttling 0e4b01df8659 had a bunch of fixups to use the right division method. However, it seems that after all that it still wasn't right -- div_u64 takes a 32-bit divisor. The headroom is still large (2^32 pages), so on mundane systems you won't hit this, but this should definitely be fixed. Link: http://lkml.kernel.org/r/80780887060514967d414b3cd91f9a316a16ab98.1584036142.git.chris@xxxxxxxxxxxxxx Fixes: 0e4b01df8659 ("mm, memcg: throttle allocators when failing reclaim over memory.high") Signed-off-by: Chris Down <chris@xxxxxxxxxxxxxx> Reported-by: Johannes Weiner <hannes@xxxxxxxxxxx> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Tejun Heo <tj@xxxxxxxxxx> Cc: Roman Gushchin <guro@xxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Nathan Chancellor <natechancellor@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> [5.4.x+] Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/memcontrol.c~mm-memcg-fix-corruption-on-64-bit-divisor-in-memoryhigh-throttling +++ a/mm/memcontrol.c @@ -2339,7 +2339,7 @@ void mem_cgroup_handle_over_high(void) */ clamped_high = max(high, 1UL); - overage = div_u64((u64)(usage - high) << MEMCG_DELAY_PRECISION_SHIFT, + overage = div64_u64((u64)(usage - high) << MEMCG_DELAY_PRECISION_SHIFT, clamped_high); penalty_jiffies = ((u64)overage * overage * HZ) _
