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Subject: Re: UBSAN: Undefined behaviour in mm/page_alloc.c
To:     Michal Hocko <mhocko@kernel.org>
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        Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
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From:   Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
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Date:   Fri, 9 Nov 2018 19:07:49 +0900
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On 2018/11/09 18:56, Michal Hocko wrote:
> Does this following look better?

Yes.

>> Also, why not to add BUG_ON(gfp_mask & __GFP_NOFAIL); here?
> 
> Because we do not want to blow up the kernel just because of a stupid
> usage of the allocator. Can you think of an example where it would
> actually make any sense?
> 
> I would argue that such a theoretical abuse would blow up on an
> unchecked NULL ptr access. Isn't that enough?

We after all can't avoid blowing up the kernel even if we don't add BUG_ON().
Stopping with BUG_ON() is saner than NULL pointer dereference messages.