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=-17.4 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 4AC2DC433E0 for ; Tue, 16 Jun 2020 12:56:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 21E9E20B1F for ; Tue, 16 Jun 2020 12:56:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="sSHE2J4H" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728160AbgFPM4f (ORCPT ); Tue, 16 Jun 2020 08:56:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48118 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725901AbgFPM4d (ORCPT ); Tue, 16 Jun 2020 08:56:33 -0400 Received: from mail-qt1-x849.google.com (mail-qt1-x849.google.com [IPv6:2607:f8b0:4864:20::849]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 99D33C061573 for ; Tue, 16 Jun 2020 05:56:33 -0700 (PDT) Received: by mail-qt1-x849.google.com with SMTP id d2so16652641qtw.4 for ; Tue, 16 Jun 2020 05:56:33 -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=JEQhTwQYPsGwAzZzLRu7bODyjB8wxGLamvh49Pujfk0=; b=sSHE2J4HPUB3tIDmmWhIklNcdHKql+Uyvzmc6XqZpJzmMGO9f6RWeMHzZrA6nd1tSH wMFPzYcAPkUjWTpoSnXWYqcJagGQ/qjFYIRVjH2z9YI/HeVHHQV5Pl3ZS6vTxa7SGj5L j+utHFL7hNCvLLPoFB+AbBI8rZHh9d4+uQVvgsOqCTpmGC27qch98mbMkhW9CKDfvNJ8 c1NsXeSe3lzWr+2hbz2PjJhuS2gJbX8ZKdgrN0uNsF4RMooNpcflAm1VQJlWZ+0I9jie 0V6sIasNyxIBD6XERhgR0uOqbXiop7Ciwfj1E4eOd1HPeB+YNnkWvso/1bDHoPZ3yCxp kg8w== 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=JEQhTwQYPsGwAzZzLRu7bODyjB8wxGLamvh49Pujfk0=; b=raZRygRs7hzzyj7VQrxroBF0+K2hBZPfQGadIDHKu6eqFWlJ8YdQ/4FWaoy/UtBVj4 JpyGuWALEr6hCbjsPMIN+Nhv8PJIGLCeVWTZ637abt6e4yQdfL9a84N+/IgAubIVYWzq Ex0rp+XilR57dx5DP0mzZ8TrWWVKLngfEn12GsEW0oXTPeRy1oKqRYrvjahP5tie/QnR PoL5dwjJPLIhrwpcpkxsVuAs78Q3B2I8IcgtgLSlvqkTT0E288VUsmIJnRY/VSeDbczv DXFRjxuGxl5p/MptWXLjS2TsbO625SfsIsMpy+PbMY4D5OXIbd04FQrvqQgjVyMpOw56 s62g== X-Gm-Message-State: AOAM531C08HqF9tXErSREP96xwUthGdR5XpI3DUcebycmxRhqvXEm3YC FaMkiCFcT7UacKjvAVFepVUX1iJuWQ== X-Google-Smtp-Source: ABdhPJwJECfqDtEzlbRiaVbG9X3exdfTM0hZYMe8eM3LQl2bahV0IpaKa5NjpgAs6dfyJ1u5JrhunEnOKA== X-Received: by 2002:a0c:e5c1:: with SMTP id u1mr2081593qvm.140.1592312191743; Tue, 16 Jun 2020 05:56:31 -0700 (PDT) Date: Tue, 16 Jun 2020 14:56:17 +0200 Message-Id: <20200616125617.237428-1-elver@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.27.0.290.gba653c62da-goog Subject: [PATCH] mm, kcsan: Instrument SLAB/SLUB free with "ASSERT_EXCLUSIVE_ACCESS" From: Marco Elver To: elver@google.com, akpm@linux-foundation.org Cc: 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 --- mm/slab.c | 4 ++++ mm/slub.c | 4 ++++ 2 files changed, 8 insertions(+) diff --git a/mm/slab.c b/mm/slab.c index 9350062ffc1a..4c7013eeacd9 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -3426,6 +3426,10 @@ 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. */ + __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..57db6ca2e0dc 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1470,6 +1470,10 @@ 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. */ + __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_); } -- 2.27.0.290.gba653c62da-goog