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 76697C43460 for ; Fri, 30 Apr 2021 05:59:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 51B02613A9 for ; Fri, 30 Apr 2021 05:59:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230286AbhD3GAg (ORCPT ); Fri, 30 Apr 2021 02:00:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:53836 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230280AbhD3GAf (ORCPT ); Fri, 30 Apr 2021 02:00:35 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5F2536147E; Fri, 30 Apr 2021 05:59:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1619762386; bh=Qzgh6fard9AtLUmTW/4xzZxidPIS98HeJzwg2Gsv4qg=; h=Date:From:To:Subject:In-Reply-To:From; b=hbgg9Ws56k8/+H0pJPc9/JSlolbjEy+tPlBOQ8qZz2HJnghZba6WbmUoVuxLshAaS zysFkvyqFHJDT+sV1KDaRrV3PHykczdRTtwAnNXcIOk98JcviyZPT0AIxo2iJOSSZo tLfiFdTvpj17Mid7Iytg1bP6WSTFgNLmwfOEufFw= Date: Thu, 29 Apr 2021 22:59:46 -0700 From: Andrew Morton To: akpm@linux-foundation.org, andreyknvl@gmail.com, dvyukov@google.com, elver@google.com, eugenis@google.com, glider@google.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, pcc@google.com, torvalds@linux-foundation.org Subject: [patch 128/178] kasan: fix kasan_byte_accessible() to be consistent with actual checks Message-ID: <20210430055946.mvvemtpUY%akpm@linux-foundation.org> In-Reply-To: <20210429225251.02b6386d21b69255b4f6c163@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: Peter Collingbourne Subject: kasan: fix kasan_byte_accessible() to be consistent with actual checks We can sometimes end up with kasan_byte_accessible() being called on non-slab memory. For example ksize() and krealloc() may end up calling it on KFENCE allocated memory. In this case the memory will be tagged with KASAN_SHADOW_INIT, which a subsequent patch ("kasan: initialize shadow to TAG_INVALID for SW_TAGS") will set to the same value as KASAN_TAG_INVALID, causing kasan_byte_accessible() to fail when called on non-slab memory. This highlighted the fact that the check in kasan_byte_accessible() was inconsistent with checks as implemented for loads and stores (kasan_check_range() in SW tags mode and hardware-implemented checks in HW tags mode). kasan_check_range() does not have a check for KASAN_TAG_INVALID, and instead has a comparison against KASAN_SHADOW_START. In HW tags mode, we do not have either, but we do set TCR_EL1.TCMA which corresponds with the comparison against KASAN_TAG_KERNEL. Therefore, update kasan_byte_accessible() for both SW and HW tags modes to correspond with the respective checks on loads and stores. Link: https://linux-review.googlesource.com/id/Ic6d40803c57dcc6331bd97fbb9a60b0d38a65a36 Link: https://lkml.kernel.org/r/20210405220647.1965262-1-pcc@google.com Signed-off-by: Peter Collingbourne Reviewed-by: Andrey Konovalov Reviewed-by: Marco Elver Cc: Dmitry Vyukov Cc: Alexander Potapenko Cc: Peter Collingbourne Cc: Evgenii Stepanov Signed-off-by: Andrew Morton --- mm/kasan/kasan.h | 3 +-- mm/kasan/sw_tags.c | 10 +++++++--- 2 files changed, 8 insertions(+), 5 deletions(-) --- a/mm/kasan/kasan.h~kasan-fix-kasan_byte_accessible-to-be-consistent-with-actual-checks +++ a/mm/kasan/kasan.h @@ -396,8 +396,7 @@ static inline bool kasan_byte_accessible u8 ptr_tag = get_tag(addr); u8 mem_tag = hw_get_mem_tag((void *)addr); - return (mem_tag != KASAN_TAG_INVALID) && - (ptr_tag == KASAN_TAG_KERNEL || ptr_tag == mem_tag); + return ptr_tag == KASAN_TAG_KERNEL || ptr_tag == mem_tag; } #else /* CONFIG_KASAN_HW_TAGS */ --- a/mm/kasan/sw_tags.c~kasan-fix-kasan_byte_accessible-to-be-consistent-with-actual-checks +++ a/mm/kasan/sw_tags.c @@ -121,10 +121,14 @@ bool kasan_check_range(unsigned long add bool kasan_byte_accessible(const void *addr) { u8 tag = get_tag(addr); - u8 shadow_byte = READ_ONCE(*(u8 *)kasan_mem_to_shadow(kasan_reset_tag(addr))); + void *untagged_addr = kasan_reset_tag(addr); + u8 shadow_byte; - return (shadow_byte != KASAN_TAG_INVALID) && - (tag == KASAN_TAG_KERNEL || tag == shadow_byte); + if (untagged_addr < kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) + return false; + + shadow_byte = READ_ONCE(*(u8 *)kasan_mem_to_shadow(untagged_addr)); + return tag == KASAN_TAG_KERNEL || tag == shadow_byte; } #define DEFINE_HWASAN_LOAD_STORE(size) \ _