| Message ID | 80780887060514967d414b3cd91f9a316a16ab98.1584036142.git.chris@chrisdown.name (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] mm, memcg: Fix corruption on 64-bit divisor in memory.high throttling | expand |
On Thu, Mar 12, 2020 at 06:02:54PM +0000, Chris Down wrote: > 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. > > Fixes: 0e4b01df8659 ("mm, memcg: throttle allocators when failing reclaim over memory.high") > Reported-by: Johannes Weiner <hannes@cmpxchg.org> > Signed-off-by: Chris Down <chris@chrisdown.name> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Tejun Heo <tj@kernel.org> > Cc: linux-mm@kvack.org > Cc: cgroups@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Cc: kernel-team@fb.com > Cc: stable@vger.kernel.org # 5.4.x div_u64 versus div64_u64 is really a handgrenade. We just fixed a bunch of those in psi as well. Acked-by: Johannes Weiner <hannes@cmpxchg.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 63bb6a2aab81..a70206e516fe 100644 --- a/mm/memcontrol.c +++ b/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)
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. Fixes: 0e4b01df8659 ("mm, memcg: throttle allocators when failing reclaim over memory.high") Reported-by: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Chris Down <chris@chrisdown.name> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Tejun Heo <tj@kernel.org> Cc: linux-mm@kvack.org Cc: cgroups@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: kernel-team@fb.com Cc: stable@vger.kernel.org # 5.4.x --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)