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=-15.8 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_RED 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 3755BC433E4 for ; Thu, 25 Mar 2021 04:38:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1CC4B61A23 for ; Thu, 25 Mar 2021 04:38:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229760AbhCYEhm (ORCPT ); Thu, 25 Mar 2021 00:37:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:44130 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229782AbhCYEhV (ORCPT ); Thu, 25 Mar 2021 00:37:21 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6471961A1D; Thu, 25 Mar 2021 04:37:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1616647040; bh=gaT8IEf8GSnOVlU+YJoOeQRqSYnOUvFmFL7h2HDMNqY=; h=Date:From:To:Subject:In-Reply-To:From; b=oe9U54k7tqzjkW/1M3a6SkxHoi9NE1JY87SWrhTX0iD7VHZsbQrlXfpU11tipPg7O IJ+K5FfP27p2um83GjxdYmj5EOsZIDn5Mr0LNXfxh7WL2U62ZPvOTSOzFvLr6dRfWk 3iCtsRxlqPXHQGJpjfGZJ5UJ8DcGShhsFid0Dil0= Date: Wed, 24 Mar 2021 21:37:20 -0700 From: Andrew Morton To: akpm@linux-foundation.org, andreyknvl@google.com, aryabinin@virtuozzo.com, Branislav.Rankov@arm.com, catalin.marinas@arm.com, dvyukov@google.com, elver@google.com, eugenis@google.com, glider@google.com, kevin.brodsky@arm.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, pcc@google.com, stable@vger.kernel.org, torvalds@linux-foundation.org, vincenzo.frascino@arm.com, will.deacon@arm.com Subject: [patch 02/14] kasan: fix per-page tags for non-page_alloc pages Message-ID: <20210325043720.fMMODU8WV%akpm@linux-foundation.org> In-Reply-To: <20210324213644.bf03a529aec4ef9580e17dbc@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: Andrey Konovalov Subject: kasan: fix per-page tags for non-page_alloc pages To allow performing tag checks on page_alloc addresses obtained via page_address(), tag-based KASAN modes store tags for page_alloc allocations in page->flags. Currently, the default tag value stored in page->flags is 0x00. Therefore, page_address() returns a 0x00ffff... address for pages that were not allocated via page_alloc. This might cause problems. A particular case we encountered is a conflict with KFENCE. If a KFENCE-allocated slab object is being freed via kfree(page_address(page) + offset), the address passed to kfree() will get tagged with 0x00 (as slab pages keep the default per-page tags). This leads to is_kfence_address() check failing, and a KFENCE object ending up in normal slab freelist, which causes memory corruptions. This patch changes the way KASAN stores tag in page-flags: they are now stored xor'ed with 0xff. This way, KASAN doesn't need to initialize per-page flags for every created page, which might be slow. With this change, page_address() returns natively-tagged (with 0xff) pointers for pages that didn't have tags set explicitly. This patch fixes the encountered conflict with KFENCE and prevents more similar issues that can occur in the future. Link: https://lkml.kernel.org/r/1a41abb11c51b264511d9e71c303bb16d5cb367b.1615475452.git.andreyknvl@google.com Fixes: 2813b9c02962 ("kasan, mm, arm64: tag non slab memory allocated via pagealloc") Signed-off-by: Andrey Konovalov Reviewed-by: Marco Elver Cc: Catalin Marinas Cc: Will Deacon Cc: Vincenzo Frascino Cc: Dmitry Vyukov Cc: Andrey Ryabinin Cc: Alexander Potapenko Cc: Peter Collingbourne Cc: Evgenii Stepanov Cc: Branislav Rankov Cc: Kevin Brodsky Cc: Signed-off-by: Andrew Morton --- include/linux/mm.h | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) --- a/include/linux/mm.h~kasan-fix-per-page-tags-for-non-page_alloc-pages +++ a/include/linux/mm.h @@ -1461,16 +1461,28 @@ static inline bool cpupid_match_pid(stru #if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS) +/* + * KASAN per-page tags are stored xor'ed with 0xff. This allows to avoid + * setting tags for all pages to native kernel tag value 0xff, as the default + * value 0x00 maps to 0xff. + */ + static inline u8 page_kasan_tag(const struct page *page) { - if (kasan_enabled()) - return (page->flags >> KASAN_TAG_PGSHIFT) & KASAN_TAG_MASK; - return 0xff; + u8 tag = 0xff; + + if (kasan_enabled()) { + tag = (page->flags >> KASAN_TAG_PGSHIFT) & KASAN_TAG_MASK; + tag ^= 0xff; + } + + return tag; } static inline void page_kasan_tag_set(struct page *page, u8 tag) { if (kasan_enabled()) { + tag ^= 0xff; page->flags &= ~(KASAN_TAG_MASK << KASAN_TAG_PGSHIFT); page->flags |= (tag & KASAN_TAG_MASK) << KASAN_TAG_PGSHIFT; } _