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=-7.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 CE934C433E0 for ; Fri, 7 Aug 2020 06:19:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD0F42177B for ; Fri, 7 Aug 2020 06:19:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596781154; bh=2UE3dQE/YR8k4zIoUAYLHNZ1AerjcU14FqZxzHA1uEE=; h=Date:From:To:Subject:In-Reply-To:Reply-To:List-ID:From; b=tHTpbQqK7bXEEbzXciw/JKsfqbpszRJcCLYS3rgqImgw76yz91Axjy/sKSNmG51tb ylRkRQoUMUFwcbj2Z4b5WlT+jkRyExzW9dcLwMJKjaFnAmX6II2m9fzlvItlssxFjo 6JuTaae6lihjLznDJV4ixuG/DMMh3czZoJmLcd5M= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726038AbgHGGTO (ORCPT ); Fri, 7 Aug 2020 02:19:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:54762 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725379AbgHGGTO (ORCPT ); Fri, 7 Aug 2020 02:19:14 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 36B6722CAF; Fri, 7 Aug 2020 06:19:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596781153; bh=2UE3dQE/YR8k4zIoUAYLHNZ1AerjcU14FqZxzHA1uEE=; h=Date:From:To:Subject:In-Reply-To:From; b=0K1uw6CgAKdDBpkkaQoF6X23Dm+oxYxzfkfrGGQtXSoaJ2Uw73n8Mc/h02cDUVzxe mo0z78fhfArfol1fxuiUmhUWQ/KhObAofJk40A2qdnF92MQ8FH4HGwbUq+hclZTjCk v8D/rnmKx0hH9QwECG4miQNd5UAONdC2jvzyzoQM= Date: Thu, 06 Aug 2020 23:19:12 -0700 From: Andrew Morton To: akpm@linux-foundation.org, andreyknvl@google.com, cl@linux.com, elver@google.com, glider@google.com, iamjoonsoo.kim@lge.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, penberg@kernel.org, rientjes@google.com, torvalds@linux-foundation.org Subject: [patch 039/163] mm, kcsan: instrument SLAB/SLUB free with "ASSERT_EXCLUSIVE_ACCESS" Message-ID: <20200807061912.r0alqJmL-%akpm@linux-foundation.org> In-Reply-To: <20200806231643.a2711a608dd0f18bff2caf2b@linux-foundation.org> User-Agent: s-nail v14.8.16 Sender: mm-commits-owner@vger.kernel.org Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Marco Elver Subject: mm, kcsan: instrument SLAB/SLUB free with "ASSERT_EXCLUSIVE_ACCESS" Provide the necessary KCSAN checks to assist with debugging racy use-after-frees. While KASAN is more reliable at generally catching such use-after-frees (due to its use of a quarantine), it can be difficult to debug racy use-after-frees. If a reliable reproducer exists, KCSAN can assist in debugging such issues. Note: ASSERT_EXCLUSIVE_ACCESS is a convenience wrapper if the size is simply sizeof(var). Instead, here we just use __kcsan_check_access() explicitly to pass the correct size. Link: http://lkml.kernel.org/r/20200623072653.114563-1-elver@google.com Signed-off-by: Marco Elver Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton --- mm/slab.c | 5 +++++ mm/slub.c | 5 +++++ 2 files changed, 10 insertions(+) --- a/mm/slab.c~mm-kcsan-instrument-slab-slub-free-with-assert_exclusive_access +++ a/mm/slab.c @@ -3432,6 +3432,11 @@ static __always_inline void __cache_free if (kasan_slab_free(cachep, objp, _RET_IP_)) return; + /* Use KCSAN to help debug racy use-after-free. */ + if (!(cachep->flags & SLAB_TYPESAFE_BY_RCU)) + __kcsan_check_access(objp, cachep->object_size, + KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ASSERT); + ___cache_free(cachep, objp, caller); } --- a/mm/slub.c~mm-kcsan-instrument-slab-slub-free-with-assert_exclusive_access +++ a/mm/slub.c @@ -1549,6 +1549,11 @@ static __always_inline bool slab_free_ho if (!(s->flags & SLAB_DEBUG_OBJECTS)) debug_check_no_obj_freed(x, s->object_size); + /* Use KCSAN to help debug racy use-after-free. */ + if (!(s->flags & SLAB_TYPESAFE_BY_RCU)) + __kcsan_check_access(x, s->object_size, + KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ASSERT); + /* KASAN might put x into memory quarantine, delaying its reuse */ return kasan_slab_free(s, x, _RET_IP_); } _