From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5CA5FC2BB48 for ; Tue, 15 Dec 2020 03:15:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 39CD82247F for ; Tue, 15 Dec 2020 03:15:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728095AbgLODOq (ORCPT ); Mon, 14 Dec 2020 22:14:46 -0500 Received: from mail.kernel.org ([198.145.29.99]:42344 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727803AbgLODOY (ORCPT ); Mon, 14 Dec 2020 22:14:24 -0500 Date: Mon, 14 Dec 2020 19:13:41 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1608002023; bh=qGt8F2fqaDvZFHC17GJMmOy1PWyjSbcWQR4KVvWIuM4=; h=From:To:Subject:In-Reply-To:From; b=wqGYwKbKeNQzN/6MtHDW6kfRds2kryBbH1bbzJNp/sZmWBQgZhkOWfI0Bw0oe7Btv r5OTIm3vROVsQCyl6X8NjEdzcs5Rxb+RlproTIFCt9p7nmDQB2DQesKzKPuz4YIY0X EmoSjd0wwVwVsmdwyzffpMwWdGu3QNTX+ODJNLps= From: Andrew Morton To: akpm@linux-foundation.org, david@redhat.com, glider@google.com, keescook@chromium.org, labbott@kernel.org, linux-mm@kvack.org, mateusznosek0@gmail.com, mhocko@kernel.org, mm-commits@vger.kernel.org, rafael.j.wysocki@intel.com, rppt@linux.ibm.com, torvalds@linux-foundation.org, vbabka@suse.cz Subject: [patch 177/200] mm, page_poison: remove CONFIG_PAGE_POISONING_NO_SANITY Message-ID: <20201215031341.0XN-lrX23%akpm@linux-foundation.org> In-Reply-To: <20201214190237.a17b70ae14f129e2dca3d204@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Vlastimil Babka Subject: mm, page_poison: remove CONFIG_PAGE_POISONING_NO_SANITY CONFIG_PAGE_POISONING_NO_SANITY skips the check on page alloc whether the poison pattern was corrupted, suggesting a use-after-free. The motivation to introduce it in commit 8823b1dbc05f ("mm/page_poison.c: enable PAGE_POISONING as a separate option") was to simply sanitize freed pages, optimally together with CONFIG_PAGE_POISONING_ZERO. These days we have an init_on_free=1 boot option, which makes this use case of page poisoning redundant. For sanitizing, writing zeroes is sufficient, there is pretty much no benefit from writing the 0xAA poison pattern to freed pages, without checking it back on alloc. Thus, remove this option and suggest init_on_free instead in the main config's help. Link: https://lkml.kernel.org/r/20201113104033.22907-5-vbabka@suse.cz Signed-off-by: Vlastimil Babka Acked-by: David Hildenbrand Cc: Mike Rapoport Cc: Rafael J. Wysocki Cc: Alexander Potapenko Cc: Kees Cook Cc: Laura Abbott Cc: Mateusz Nosek Cc: Michal Hocko Signed-off-by: Andrew Morton --- drivers/virtio/virtio_balloon.c | 4 +--- mm/Kconfig.debug | 15 ++++----------- mm/page_poison.c | 3 --- 3 files changed, 5 insertions(+), 17 deletions(-) --- a/drivers/virtio/virtio_balloon.c~mm-page_poison-remove-config_page_poisoning_no_sanity +++ a/drivers/virtio/virtio_balloon.c @@ -1114,9 +1114,7 @@ static int virtballoon_validate(struct v * page reporting as it could potentially change the contents * of our free pages. */ - if (!want_init_on_free() && - (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) || - !page_poisoning_enabled_static())) + if (!want_init_on_free() && !page_poisoning_enabled_static()) __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON); else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING); --- a/mm/Kconfig.debug~mm-page_poison-remove-config_page_poisoning_no_sanity +++ a/mm/Kconfig.debug @@ -74,18 +74,11 @@ config PAGE_POISONING Note that "poison" here is not the same thing as the "HWPoison" for CONFIG_MEMORY_FAILURE. This is software poisoning only. - If unsure, say N - -config PAGE_POISONING_NO_SANITY - depends on PAGE_POISONING - bool "Only poison, don't sanity check" - help - Skip the sanity checking on alloc, only fill the pages with - poison on free. This reduces some of the overhead of the - poisoning feature. + If you are only interested in sanitization of freed pages without + checking the poison pattern on alloc, you can boot the kernel with + "init_on_free=1" instead of enabling this. - If you are only interested in sanitization, say Y. Otherwise - say N. + If unsure, say N config PAGE_POISONING_ZERO bool "Use zero for poisoning instead of debugging value" --- a/mm/page_poison.c~mm-page_poison-remove-config_page_poisoning_no_sanity +++ a/mm/page_poison.c @@ -51,9 +51,6 @@ static void check_poison_mem(unsigned ch unsigned char *start; unsigned char *end; - if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY)) - return; - start = memchr_inv(mem, PAGE_POISON, bytes); if (!start) return; _