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bh=mZUUqDVmjnQcz5ki8ID/5GhTPms3yRpD6egNZ7qELyw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=uL4ubQEsvjb5ruxhzanTCIFfc+To+PV5PK8wMHyR+H268suW+RQcJ/LptTWdF26Ck esfiB9T8BxJlJOB9VhSxF08u7Slygi/DWM25Qh78NPFOh8WcpRmuc1eOxxSO1RdhfT S5hKKQp75KI0A4PS+aYDAdLUFWdiBAKxbR1HxE3s= Date: Wed, 8 Mar 2023 17:46:08 -0800 From: Andrew Morton To: Peter Collingbourne Cc: catalin.marinas@arm.com, andreyknvl@gmail.com, linux-mm@kvack.org, kasan-dev@googlegroups.com, ryabinin.a.a@gmail.com, linux-arm-kernel@lists.infradead.org, vincenzo.frascino@arm.com, will@kernel.org, eugenis@google.com, stable@vger.kernel.org Subject: Re: [PATCH v3 1/2] Revert "kasan: drop skip_kasan_poison variable in free_pages_prepare" Message-Id: <20230308174608.e66ed98c97ea29934d99c596@linux-foundation.org> In-Reply-To: <20230301003545.282859-2-pcc@google.com> References: <20230301003545.282859-1-pcc@google.com> <20230301003545.282859-2-pcc@google.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 27D95140011 X-Stat-Signature: 4k8cswtfjf9n7iugpcx9mpshwjtn5ee7 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1678326372-340082 X-HE-Meta: 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 /yxwX5ts 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 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 Tue, 28 Feb 2023 16:35:44 -0800 Peter Collingbourne wrote: > This reverts commit 487a32ec24be819e747af8c2ab0d5c515508086a. > > The should_skip_kasan_poison() function reads the PG_skip_kasan_poison > flag from page->flags. However, this line of code in free_pages_prepare(): > > page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; > > clears most of page->flags, including PG_skip_kasan_poison, before calling > should_skip_kasan_poison(), which meant that it would never return true > as a result of the page flag being set. Therefore, fix the code to call > should_skip_kasan_poison() before clearing the flags, as we were doing > before the reverted patch. What are the user visible effects of this change? > Cc: # 6.1 Especially if it's cc:stable. Thanks.