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 autolearn=ham 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 E1497C433B4 for ; Fri, 30 Apr 2021 05:59:48 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 936D561481 for ; Fri, 30 Apr 2021 05:59:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 936D561481 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 387C6940022; Fri, 30 Apr 2021 01:59:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 35F888D000B; Fri, 30 Apr 2021 01:59:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1D9E9940022; Fri, 30 Apr 2021 01:59:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0252.hostedemail.com [216.40.44.252]) by kanga.kvack.org (Postfix) with ESMTP id 0229F8D000B for ; Fri, 30 Apr 2021 01:59:47 -0400 (EDT) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id BCAA1181AF5C3 for ; Fri, 30 Apr 2021 05:59:47 +0000 (UTC) X-FDA: 78087982014.19.4F4C67E Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf20.hostedemail.com (Postfix) with ESMTP id EF4CD3C7 for ; Fri, 30 Apr 2021 05:59:38 +0000 (UTC) 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 Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=hbgg9Ws5; dmarc=none; spf=pass (imf20.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Rspamd-Server: rspam03 X-Stat-Signature: 4tdesnmg1we5dbh7jr17ao9q96ce5juu X-Rspamd-Queue-Id: EF4CD3C7 Received-SPF: none (linux-foundation.org>: No applicable sender policy available) receiver=imf20; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1619762378-822227 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: 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) \ _