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=-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 97B2BC48BE8 for ; Wed, 16 Jun 2021 01:23:29 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4BCED613B9 for ; Wed, 16 Jun 2021 01:23:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4BCED613B9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E3B1C6B0073; Tue, 15 Jun 2021 21:23:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DEAEE6B0074; Tue, 15 Jun 2021 21:23:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C64826B0075; Tue, 15 Jun 2021 21:23:28 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0054.hostedemail.com [216.40.44.54]) by kanga.kvack.org (Postfix) with ESMTP id 93DA76B0073 for ; Tue, 15 Jun 2021 21:23:28 -0400 (EDT) Received: from smtpin29.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 313BD181AC9C6 for ; Wed, 16 Jun 2021 01:23:28 +0000 (UTC) X-FDA: 78257839296.29.AC3B77F Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf07.hostedemail.com (Postfix) with ESMTP id 9F8FFA0001CF for ; Wed, 16 Jun 2021 01:23:17 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 93138613B1; Wed, 16 Jun 2021 01:23:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1623806607; bh=iuk25coWgG0AAs1zL64BHgOLlaQBlGSxs8NbXFzAd7c=; h=Date:From:To:Subject:In-Reply-To:From; b=wUQVJJWLDvag7HuirUUUv5eApobvME8tDFcmU3XK8mEyFAVn5dNGf0lNTLwcPbc+r XT+wq1a5V7V1xm5c5sDn6ZMi8D56KTefFGZS9aPHpwHdfkcmi6Zr57midAmG0QylQV ihwujzUenl8lOjhLLvp/+978pIfiJvgd36QH3TJY= Date: Tue, 15 Jun 2021 18:23:26 -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 05/18] mm/slub: actually fix freelist pointer vs redzoning Message-ID: <20210616012326.IlNBEvZ__%akpm@linux-foundation.org> In-Reply-To: <20210615182248.9a0ba90e8e66b9f4a53c0d23@linux-foundation.org> User-Agent: s-nail v14.8.16 Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=wUQVJJWL; spf=pass (imf07.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Stat-Signature: r67crmdd9twpb96kp5ppbdbj1bdakp1m X-Rspamd-Queue-Id: 9F8FFA0001CF X-Rspamd-Server: rspam06 X-HE-Tag: 1623806597-920000 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Kees Cook Subject: mm/slub: actually fix freelist pointer vs redzoning It turns out that SLUB redzoning ("slub_debug=Z") checks from s->object_size rather than from s->inuse (which is normally bumped to make room for the freelist pointer), so a cache created with an object size less than 24 would have the freelist pointer written beyond s->object_size, causing the redzone to be corrupted by the freelist pointer. This was very visible with "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____): 00 00 00 00 00 f6 f4 a5 ........ Redzone (____ptrval____): 40 1d e8 1a aa @.... Padding (____ptrval____): 00 00 00 00 00 00 00 00 ........ Adjust the offset to stay within s->object_size. (Note that no caches of in this size range are known to exist in the kernel currently.) Link: https://lkml.kernel.org/r/20210608183955.280836-4-keescook@chromium.org Link: https://lore.kernel.org/linux-mm/20200807160627.GA1420741@elver.google.com/ Link: https://lore.kernel.org/lkml/0f7dd7b2-7496-5e2d-9488-2ec9f8e90441@suse.cz/Fixes: 89b83f282d8b (slub: avoid redzone when choosing freepointer location) Link: https://lore.kernel.org/lkml/CANpmjNOwZ5VpKQn+SYWovTkFB4VsT-RPwyENBmaK0dLcpqStkA@mail.gmail.com Signed-off-by: Kees Cook Reported-by: Marco Elver Reported-by: "Lin, Zhenpeng" Tested-by: Marco Elver Acked-by: Vlastimil Babka Cc: Christoph Lameter Cc: David Rientjes Cc: Joonsoo Kim Cc: Pekka Enberg Cc: Roman Gushchin Cc: Signed-off-by: Andrew Morton --- mm/slub.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-) --- a/mm/slub.c~mm-slub-actually-fix-freelist-pointer-vs-redzoning +++ a/mm/slub.c @@ -3689,7 +3689,6 @@ static int calculate_sizes(struct kmem_c { slab_flags_t flags = s->flags; unsigned int size = s->object_size; - unsigned int freepointer_area; unsigned int order; /* @@ -3698,13 +3697,6 @@ static int calculate_sizes(struct kmem_c * the possible location of the free pointer. */ size = ALIGN(size, sizeof(void *)); - /* - * This is the area of the object where a freepointer can be - * safely written. If redzoning adds more to the inuse size, we - * can't use that portion for writing the freepointer, so - * s->offset must be limited within this for the general case. - */ - freepointer_area = size; #ifdef CONFIG_SLUB_DEBUG /* @@ -3730,7 +3722,7 @@ static int calculate_sizes(struct kmem_c /* * With that we have determined the number of bytes in actual use - * by the object. This is the potential offset to the free pointer. + * by the object and redzoning. */ s->inuse = size; @@ -3753,13 +3745,13 @@ static int calculate_sizes(struct kmem_c */ s->offset = size; size += sizeof(void *); - } else if (freepointer_area > sizeof(void *)) { + } else { /* * Store freelist pointer near middle of object to keep * it away from the edges of the object to avoid small * sized over/underflows from neighboring allocations. */ - s->offset = ALIGN(freepointer_area / 2, sizeof(void *)); + s->offset = ALIGN_DOWN(s->object_size / 2, sizeof(void *)); } #ifdef CONFIG_SLUB_DEBUG _