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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 14A55C4321E for ; Tue, 29 Nov 2022 12:04:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233909AbiK2ME0 (ORCPT ); Tue, 29 Nov 2022 07:04:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35364 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233500AbiK2MDt (ORCPT ); Tue, 29 Nov 2022 07:03:49 -0500 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7BFBE532DA for ; Tue, 29 Nov 2022 04:02:53 -0800 (PST) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id D21F021A9D; Tue, 29 Nov 2022 12:02:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1669723371; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=z/3hsjogRyiywNOtVq13TN6FozNI4uz7VCcPb28njoU=; b=qqpcbvqqo4tXUVc7mA+18PQYvRcs7oDUpGh/g3Up9IsTr804a/89Jyltjdt0zIJEFsGBZL UsLIyrtQcgG9dfy2KjHa8Ar0QoZgz5ZSycs4s5owWC1PuOg0+F3YPJIdktCFL+iUK0W2Yh jxLY53OWK5LF1Tv7U0fwPq+JKpUtHdw= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1669723371; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=z/3hsjogRyiywNOtVq13TN6FozNI4uz7VCcPb28njoU=; b=UcQe1LxJo8la8OZ6DKqZjiM5CfBtE6Zb/LqKvfCRlOw5VE/1x5802P26oq+jYQSHBp+sfX rPgRrFVUpemBMDAw== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id A54C013428; Tue, 29 Nov 2022 12:02:51 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id eSCJJ+v0hWNNfQAAMHmgww (envelope-from ); Tue, 29 Nov 2022 12:02:51 +0000 Message-ID: Date: Tue, 29 Nov 2022 13:02:51 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Subject: Re: [PATCH v2 2/2] mm/slub, kunit: Add a test case for kmalloc redzone check Content-Language: en-US To: Marco Elver Cc: Feng Tang , Andrew Morton , Oliver Glitta , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20221129063358.3012362-1-feng.tang@intel.com> <20221129063358.3012362-2-feng.tang@intel.com> <67e6ebce-f8cc-7d28-5e85-8a3909c2d180@suse.cz> From: Vlastimil Babka In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/29/22 12:48, Marco Elver wrote: > On Tue, 29 Nov 2022 at 12:01, Vlastimil Babka wrote: >> >> On 11/29/22 10:31, Marco Elver wrote: >> > On Tue, 29 Nov 2022 at 07:37, Feng Tang wrote: > >> For SLAB_SKIP_KFENCE, we could also add the flag after creation to avoid >> this trouble? After all there is a sysfs file to control it at runtime >> anyway (via skip_kfence_store()). >> In that case patch 1 would have to wrap kmem_cache_create() and the flag >> addition with a new function to avoid repeating. That function could also be >> adding SLAB_NO_USER_FLAGS to kmem_cache_create(), instead of the #define >> DEFAULT_FLAGS. > > I wouldn't overcomplicate it, all we need is a way to say "this flag > should not be used directly" - and only have it available via an > indirect step. Availability via sysfs is one such step. > > And for tests, there are 2 options: > > 1. we could provide a function "kmem_cache_set_test_flags(cache, > gfp_flags)" and define SLAB_TEST_FLAGS (which would include > SLAB_SKIP_KFENCE). This still allows to set it generally, but should > make abuse less likely due to the "test" in the name of that function. > > 2. just set it directly, s->flags |= SLAB_SKIP_KFENCE. > > If you're fine with #2, that seems simplest and would be my preference. Yeah, that's what I meant. But slub_kunit.c could still have own internal cache creation function so the "|SLAB_NO_USER_FLAGS" and "s->flags |= SLAB_SKIP_KFENCE" is not repeated X times. > >> For SLAB_KMALLOC there's probably no such way unless we abuse the internal >> APIs even more and call e.g. create_boot_cache() instead of >> kmem_cache_create(). But that one is __init, so probably not. If we do >> instead allow the flag, I wouldn't add it to SLAB_CORE_FLAGS but rather >> SLAB_CACHE_FLAGS and SLAB_FLAGS_PERMITTED. > > I'd probably go with the simplest solution here. Agreed.