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=-17.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT, USER_IN_DEF_DKIM_WL 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 EF140C433E2 for ; Tue, 23 Jun 2020 07:28:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CD3EB2073E for ; Tue, 23 Jun 2020 07:28:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="e7XzSW9B" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731292AbgFWH21 (ORCPT ); Tue, 23 Jun 2020 03:28:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45522 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731054AbgFWH20 (ORCPT ); Tue, 23 Jun 2020 03:28:26 -0400 Received: from mail-qv1-xf4a.google.com (mail-qv1-xf4a.google.com [IPv6:2607:f8b0:4864:20::f4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 69D67C061573 for ; Tue, 23 Jun 2020 00:28:25 -0700 (PDT) Received: by mail-qv1-xf4a.google.com with SMTP id n10so1205826qvp.17 for ; Tue, 23 Jun 2020 00:28:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=nTQWvepZzYSn4rQEU0+1xmqZl1OOXUog19hqREujmU4=; b=e7XzSW9BiALiACWkVQb7mFB8mq6jtD10kFJCz/zBWeoYyHB4MjXZv5mb3HDvr1j71/ cgtALbncqtn6Z0+DsYEIBUPB3KG3dfumqLm0/4nvNRqwmDe//6bQQeEsAb4EuErIDHrC F5KDujFk65s4f8WpCKGbF0Dz78AIJECom73qcL78UIZ6rRyPc+XmTX+uoaSgSOK2uipT IUnqmSkwigP7MpQJjKOKMGyC3duuOp07Kl8UaBG91ONMvc0oCODHAg7iIrmqdISI7pXg ibGwXhA9/6FTWCRR55quMDfGTB+Jv7KLEbaQ0vNx2FX6w5iBzvnoK5Gjq6ZqzQJPXj/q WbnA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=nTQWvepZzYSn4rQEU0+1xmqZl1OOXUog19hqREujmU4=; b=cuR+8qSTPsJTazTTnsREMLhWvPAXFWFi5qGtzBsKCTSx/ZOf3ElgeswEqHRPYMSKne BbpYPM8uAI5swMRzdbeLJLw7smfRphi0GphEU5hgMGBslfaC7vlL6ATNASnVsyy8MNmL OHFNp9UPeiXh9FmahK/GGuMpyBlfclkAKx4rf4F2BKnwevR2NEtrFcbL3+vkTPfLdNXU jEMnCHb6SmeyDr2AeCPQrR8OvVL3lXstLE6niUDUKPG4e+g6cxWlpAX4RTzXG9W386yk ZSMeQWALIk9PBJcpls6JVmY7DsgJVhCBUTkACKV2vRcGaOc7r+11Pn2k2oJ6wLe3g4KS m9HQ== X-Gm-Message-State: AOAM533z7okH80NF77QGlPG0TlCZLVA3dhckG+LR8Cv3faH10DOaEmSq hUXYzi5Vx6kby8fHXozkrspABrTK7Q== X-Google-Smtp-Source: ABdhPJwj2i8o0If+UymYmvMwr9/d224DtNwbNKtKbk/yUkG5UMMHuHoay3TWBfoyY2g3OwYvH8W1ykEufQ== X-Received: by 2002:a05:6214:8d1:: with SMTP id da17mr5298435qvb.62.1592897304605; Tue, 23 Jun 2020 00:28:24 -0700 (PDT) Date: Tue, 23 Jun 2020 09:26:54 +0200 Message-Id: <20200623072653.114563-1-elver@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.27.0.111.gc72c7da667-goog Subject: [PATCH v2] mm, kcsan: Instrument SLAB/SLUB free with "ASSERT_EXCLUSIVE_ACCESS" From: Marco Elver To: elver@google.com, akpm@linux-foundation.org Cc: paulmck@kernel.org, dvyukov@google.com, glider@google.com, andreyknvl@google.com, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Signed-off-by: Marco Elver --- v2: * SLAB_TYPESAFE_BY_RCU allows racy use after free within RCU grace period. If slab is SLAB_TYPESAFE_BY_RCU do not check access. --- mm/slab.c | 5 +++++ mm/slub.c | 5 +++++ 2 files changed, 10 insertions(+) diff --git a/mm/slab.c b/mm/slab.c index 9350062ffc1a..cba71d88e89c 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -3426,6 +3426,11 @@ static __always_inline void __cache_free(struct kmem_cache *cachep, void *objp, 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); } diff --git a/mm/slub.c b/mm/slub.c index b8f798b50d44..4a9d43fda669 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1470,6 +1470,11 @@ static __always_inline bool slab_free_hook(struct kmem_cache *s, void *x) 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_); } -- 2.27.0.111.gc72c7da667-goog