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=-9.9 required=3.0 tests=DKIMWL_WL_HIGH,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 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 142E4C433E0 for ; Wed, 17 Jun 2020 19:54:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D984021548 for ; Wed, 17 Jun 2020 19:54:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="fjNF7THt" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726969AbgFQTyF (ORCPT ); Wed, 17 Jun 2020 15:54:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53108 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726919AbgFQTx4 (ORCPT ); Wed, 17 Jun 2020 15:53:56 -0400 Received: from mail-pf1-x442.google.com (mail-pf1-x442.google.com [IPv6:2607:f8b0:4864:20::442]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CF905C061755 for ; Wed, 17 Jun 2020 12:53:55 -0700 (PDT) Received: by mail-pf1-x442.google.com with SMTP id s23so1649427pfh.7 for ; Wed, 17 Jun 2020 12:53:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=dVavS5ePbCYrK2z1L2wDQV1nTQ1HDrNhoLc61sG4Q5M=; b=fjNF7THtjmalkLduwfjs6WAcXUJ8XrLQgh8AJX/PbmUoNRwB7NJXiEnIF4/WGEgshv 0Sc3PHTV8qK08Y1adWyY7RpUt61/9K8iqxsOWwrnN8OiquPeq+5Drr0hasoLXBo3LkL9 Qyi/sIH5I2ZUP4aCOZ0r4QvPuhCN7u5xakY94= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=dVavS5ePbCYrK2z1L2wDQV1nTQ1HDrNhoLc61sG4Q5M=; b=pFvr3A9rzsMy3D28M/OihdaJZuNfrvBc76fm8Try2O1lH4E3xlRWGRaMnMqTxN68WO /XRykLA/x46+0+yMOPZiu8D5HiMLqiyBgB+uFKrqpUlA27Ft+bDl5PSVAUJg1wRncBpt 4jz41KlC0QaasXVzIzVvjb7I2SDc9FrXcoBUcn5Xyv2zYzxbg+de1ePz3TRa7cxZGMFV KzjjqhFpwiY/qhIGct1jcqNqh3pBopvVFc1C0MGf9UUtSLIC7wBGQCD4PhZ7qGcgJ2n7 pHUVrch03XSeLIZNasU2mF+Uoli8f8HlzJE7GbGXWlGdLBoFoF4eCZ4fwtR+mQAqvtoP mJ3g== X-Gm-Message-State: AOAM532DNXVkrwCZi3wuqyMIIa+lQ5zLQJMRIMi1xVkeqFORAHBr0fBY 2Fa7UHMH5eBfS/rsnrcJYTeEbQ== X-Google-Smtp-Source: ABdhPJwOg59bPWyGSiT3mjPppY6RygkG6jLQonyfdZ8GMgBRzj7URVeINwVlCe50tSbxuqAvoLP34w== X-Received: by 2002:a63:4562:: with SMTP id u34mr358332pgk.309.1592423635262; Wed, 17 Jun 2020 12:53:55 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id r4sm566043pgp.60.2020.06.17.12.53.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Jun 2020 12:53:53 -0700 (PDT) From: Kees Cook To: Andrew Morton Cc: Kees Cook , Vlastimil Babka , Roman Gushchin , Christoph Lameter , Alexander Popov , Pekka Enberg , David Rientjes , Joonsoo Kim , vinmenon@codeaurora.org, Matthew Garrett , Jann Horn , Vijayanand Jitta , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 2/2] slab: Add naive detection of double free Date: Wed, 17 Jun 2020 12:53:49 -0700 Message-Id: <20200617195349.3471794-3-keescook@chromium.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200617195349.3471794-1-keescook@chromium.org> References: <20200617195349.3471794-1-keescook@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Similar to commit ce6fa91b9363 ("mm/slub.c: add a naive detection of double free or corruption"), add a very cheap double-free check for SLAB under CONFIG_SLAB_FREELIST_HARDENED. With this added, the "SLAB_FREE_DOUBLE" LKDTM test passes under SLAB: lkdtm: Performing direct entry SLAB_FREE_DOUBLE lkdtm: Attempting double slab free ... ------------[ cut here ]------------ WARNING: CPU: 2 PID: 2193 at mm/slab.c:757 ___cache _free+0x325/0x390 Signed-off-by: Kees Cook --- mm/slab.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/mm/slab.c b/mm/slab.c index 9350062ffc1a..c4e3a194b271 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -749,6 +749,16 @@ static void drain_alien_cache(struct kmem_cache *cachep, } } +/* &alien->lock must be held by alien callers. */ +static __always_inline void __free_one(struct array_cache *ac, void *objp) +{ + /* Avoid trivial double-free. */ + if (IS_ENABLED(CONFIG_SLAB_FREELIST_HARDENED) && + WARN_ON_ONCE(ac->avail > 0 && ac->entry[ac->avail - 1] == objp)) + return; + ac->entry[ac->avail++] = objp; +} + static int __cache_free_alien(struct kmem_cache *cachep, void *objp, int node, int page_node) { @@ -767,7 +777,7 @@ static int __cache_free_alien(struct kmem_cache *cachep, void *objp, STATS_INC_ACOVERFLOW(cachep); __drain_alien_cache(cachep, ac, page_node, &list); } - ac->entry[ac->avail++] = objp; + __free_one(ac, objp); spin_unlock(&alien->lock); slabs_destroy(cachep, &list); } else { @@ -3466,7 +3476,7 @@ void ___cache_free(struct kmem_cache *cachep, void *objp, } } - ac->entry[ac->avail++] = objp; + __free_one(ac, objp); } /** -- 2.25.1