From patchwork Wed Jun 16 01:23:22 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 462093 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, URIBL_BLOCKED autolearn=unavailable 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 883CFC48BDF for ; Wed, 16 Jun 2021 01:23:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7336D613C7 for ; Wed, 16 Jun 2021 01:23:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231774AbhFPBZb (ORCPT ); Tue, 15 Jun 2021 21:25:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:39744 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230265AbhFPBZ3 (ORCPT ); Tue, 15 Jun 2021 21:25:29 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3578E61356; Wed, 16 Jun 2021 01:23:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1623806603; bh=JDA+uQj+K1d3SfrTSfO9ZzUv+CldmXRZMGxAbidp56s=; h=Date:From:To:Subject:In-Reply-To:From; b=IEaireWPGi22na24aSwrqMIPfH7JQShS37nF5Hpi5B+syAIRPUyTQemJWta9zylgm ZdqhAxBdSeAUghswITKDbyI8zGaEwgkFX/8LzqHcgPD+gV1HIPPBLGlVfZ9KfY9KnJ VDzJnGtNGqmC1LsyPCTu+Im8/VdJOpZuF9PTYhFo= Date: Tue, 15 Jun 2021 18:23:22 -0700 From: Andrew Morton To: akpm@linux-foundation.org, cl@linux.com, elver@google.com, guro@fb.com, iamjoonsoo.kim@lge.com, keescook@chromium.org, linux-mm@kvack.org, mm-commits@vger.kernel.org, penberg@kernel.org, rientjes@google.com, stable@vger.kernel.org, torvalds@linux-foundation.org, vbabka@suse.cz, zplin@psu.edu Subject: [patch 04/18] mm/slub: fix redzoning for small allocations Message-ID: <20210616012322.mtEbkr1Dt%akpm@linux-foundation.org> In-Reply-To: <20210615182248.9a0ba90e8e66b9f4a53c0d23@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Kees Cook Subject: mm/slub: fix redzoning for small allocations The redzone area for SLUB exists between s->object_size and s->inuse (which is at least the word-aligned object_size). If a cache were created with an object_size smaller than sizeof(void *), the in-object stored freelist pointer would overwrite the redzone (e.g. with boot param "slub_debug=ZF"): BUG test (Tainted: G B ): Right Redzone overwritten ----------------------------------------------------------------------------- INFO: 0xffff957ead1c05de-0xffff957ead1c05df @offset=1502. First byte 0x1a instead of 0xbb INFO: Slab 0xffffef3950b47000 objects=170 used=170 fp=0x0000000000000000 flags=0x8000000000000200 INFO: Object 0xffff957ead1c05d8 @offset=1496 fp=0xffff957ead1c0620 Redzone (____ptrval____): bb bb bb bb bb bb bb bb ........ Object (____ptrval____): f6 f4 a5 40 1d e8 ...@.. Redzone (____ptrval____): 1a aa .. Padding (____ptrval____): 00 00 00 00 00 00 00 00 ........ Store the freelist pointer out of line when object_size is smaller than sizeof(void *) and redzoning is enabled. Additionally remove the "smaller than sizeof(void *)" check under CONFIG_DEBUG_VM in kmem_cache_sanity_check() as it is now redundant: SLAB and SLOB both handle small sizes. (Note that no caches within this size range are known to exist in the kernel currently.) Link: https://lkml.kernel.org/r/20210608183955.280836-3-keescook@chromium.org Fixes: 81819f0fc828 ("SLUB core") Signed-off-by: Kees Cook Acked-by: Vlastimil Babka Cc: Christoph Lameter Cc: David Rientjes Cc: Joonsoo Kim Cc: "Lin, Zhenpeng" Cc: Marco Elver Cc: Pekka Enberg Cc: Roman Gushchin Cc: Signed-off-by: Andrew Morton --- mm/slab_common.c | 3 +-- mm/slub.c | 8 +++++--- 2 files changed, 6 insertions(+), 5 deletions(-) --- a/mm/slab_common.c~mm-slub-fix-redzoning-for-small-allocations +++ a/mm/slab_common.c @@ -97,8 +97,7 @@ EXPORT_SYMBOL(kmem_cache_size); #ifdef CONFIG_DEBUG_VM static int kmem_cache_sanity_check(const char *name, unsigned int size) { - if (!name || in_interrupt() || size < sizeof(void *) || - size > KMALLOC_MAX_SIZE) { + if (!name || in_interrupt() || size > KMALLOC_MAX_SIZE) { pr_err("kmem_cache_create(%s) integrity check failed\n", name); return -EINVAL; } --- a/mm/slub.c~mm-slub-fix-redzoning-for-small-allocations +++ a/mm/slub.c @@ -3734,15 +3734,17 @@ static int calculate_sizes(struct kmem_c */ s->inuse = size; - if (((flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) || - s->ctor)) { + if ((flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) || + ((flags & SLAB_RED_ZONE) && s->object_size < sizeof(void *)) || + s->ctor) { /* * Relocate free pointer after the object if it is not * permitted to overwrite the first word of the object on * kmem_cache_free. * * This is the case if we do RCU, have a constructor or - * destructor or are poisoning the objects. + * destructor, are poisoning the objects, or are + * redzoning an object smaller than sizeof(void *). * * The assumption that s->offset >= s->inuse means free * pointer is outside of the object is used in the