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Fri, 26 Mar 2021 08:00:45 -0700 (PDT) MIME-Version: 1.0 References: <20210326112650.307890-1-slyfox@gentoo.org> <4e23d404-5125-6c9c-4aa7-5eff0fa1ba33@redhat.com> In-Reply-To: <4e23d404-5125-6c9c-4aa7-5eff0fa1ba33@redhat.com> From: Andrey Konovalov Date: Fri, 26 Mar 2021 16:00:34 +0100 Message-ID: Subject: Re: [PATCH] mm: page_alloc: ignore init_on_free=1 for page alloc To: David Hildenbrand , Sergei Trofimovich Cc: Andrew Morton , Linux Memory Management List , LKML , Vlastimil Babka Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: uaw9zthppokhtine61xb7rb4j6yzteem X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 498B0A057 Received-SPF: none (gmail.com>: No applicable sender policy available) receiver=imf04; identity=mailfrom; envelope-from=""; helo=mail-ed1-f44.google.com; client-ip=209.85.208.44 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1616770847-535092 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 Fri, Mar 26, 2021 at 2:49 PM David Hildenbrand wrote: > > > I observed use of poisoned pages as the crash on ia64 booted with > > init_on_free=1 init_on_alloc=1 (CONFIG_PAGE_POISONING=y config). > > There pmd page contained 0xaaaaaaaa poison pages and led to early crash. > > > > The change drops the assumption that init_on_free=1 guarantees free > > pages to contain zeros. > > > > Alternative would be to make interaction between runtime poisoning and > > sanitizing options and build-time debug flags like CONFIG_PAGE_POISONING > > more coherent. I took the simpler path. > > > > I thought latest work be Vlastimil tried to tackle that. To me, it feels > like page_poison=on and init_on_free=1 should bail out and disable one > of both things. Having both at the same time doesn't sound helpful. This is exactly how it works, see init_mem_debugging_and_hardening(). Sergei, could you elaborate more on what kind of crash this patch is trying to fix? Where does it happen and why?