linux-kernel - Re: [PATCH] mm: Fix mem_cgroup_oom

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Message-Id: <73199b41-da7d-2bd5-6214-da55ab62cea9@linux.vnet.ibm.com>
Date:   Tue, 5 Sep 2017 17:54:29 +0200
From:   Laurent Dufour <ldufour@...ux.vnet.ibm.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>,
        akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: Fix mem_cgroup_oom_disable() call missing

On 05/09/2017 17:46, Kirill A. Shutemov wrote:
> On Tue, Sep 05, 2017 at 05:30:39PM +0200, Laurent Dufour wrote:
>> Seen while reading the code, in handle_mm_fault(), in the case
>> arch_vma_access_permitted() is failing the call to mem_cgroup_oom_disable()
>> is not made.
>>
>> To fix that, move the call to mem_cgroup_oom_enable() after calling
>> arch_vma_access_permitted() as it should not have entered the memcg OOM.
>>
>> Fixes: bae473a423f6 ("mm: introduce fault_env")
>> Signed-off-by: Laurent Dufour <ldufour@...ux.vnet.ibm.com>
> 
> Ouch. Sorry for this.
> 
> Acked-by: Kirill A. Shutemov <kirill@...temov.name>
> 
> Cc: stable@ is needed too.

Andrew, should I resent it with stable in copy ?

> 
> It's strange we haven't seen reports of warning from
> mem_cgroup_oom_enable().

AFAIU, arch_vma_access_permitted() is only defined for x86 and it is
failing only in the case of the protection key mismatch, not so much used
for now...

Cheers,
Laurent.