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[209.85.167.45]) by smtp.gmail.com with ESMTPSA id v3sm5009741lfo.62.2020.04.09.09.42.36 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 09 Apr 2020 09:42:36 -0700 (PDT) Received: by mail-lf1-f45.google.com with SMTP id x23so157942lfq.1 for ; Thu, 09 Apr 2020 09:42:36 -0700 (PDT) X-Received: by 2002:a19:6144:: with SMTP id m4mr99713lfk.192.1586450556113; Thu, 09 Apr 2020 09:42:36 -0700 (PDT) MIME-Version: 1.0 References: <20200408014010.80428-1-peterx@redhat.com> <20200408014010.80428-2-peterx@redhat.com> <20200409070253.GB18386@dhcp22.suse.cz> In-Reply-To: <20200409070253.GB18386@dhcp22.suse.cz> From: Linus Torvalds Date: Thu, 9 Apr 2020 09:42:20 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 1/2] mm/mempolicy: Allow lookup_node() to handle fatal signal To: Michal Hocko Cc: Peter Xu , Linux Kernel Mailing List , Linux-MM , Andrew Morton , syzbot+693dc11fcb53120b5559@syzkaller.appspotmail.com Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Apr 9, 2020 at 12:03 AM Michal Hocko wrote: > > This patch however doesn't go all the way to revert it because 0 return > value is impossible. I'm not convinced it's impossible. And if it is, then the current code is harmless. Now, I do agree that we probably should go through and clarify the whole range of different get_user_pages() cases of returning zero (or not doing so), but right now it's so confusing that I'd prefer to keep that (possibly unnecessary) belt-and-suspenders check for zero in there. If/when somebody actually does a real audit and the result is "these functions cannot return zero" and it's documented, then we can remove those checks. Ok? Linus