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 D5CDAC4708B for ; Tue, 29 Nov 2022 17:48:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235622AbiK2RsL (ORCPT ); Tue, 29 Nov 2022 12:48:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44580 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235529AbiK2RsI (ORCPT ); Tue, 29 Nov 2022 12:48:08 -0500 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7E6FA6037D for ; Tue, 29 Nov 2022 09:48:07 -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-out2.suse.de (Postfix) with ESMTPS id 28D6A1F8C0; Tue, 29 Nov 2022 17:48:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1669744086; 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=TswUKym7Ck2/WhmtiP5vVkDmiPNaof1/ApXztlLEoAk=; b=hi1tvYbGSCFucwZVfTWdxDdrdKCVMYxlwSlv+KUfmubWbujb3vVbVQBDDJbDGHF2dZUzvz 8Desv15v6GUMFcBbjGc6xmnjEsqQeFerN9K/JlJ9cuzS5NU1aHuzz9DJAOxxEOJn+D0Mhh XWsYRQQQzESwyAIpafbFAGZNfeSD0h4= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1669744086; 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=TswUKym7Ck2/WhmtiP5vVkDmiPNaof1/ApXztlLEoAk=; b=5CfbDA9QmIyMtNHjRqEk1HEkCliQ2L2DWDFwrdZ/foA/f0c7nu+MYr0D9tm2V+LVTkzDfM b8FP52LO2CiYb2Cw== 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 ED66213AF6; Tue, 29 Nov 2022 17:48:05 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id WrdmOdVFhmOTPQAAMHmgww (envelope-from ); Tue, 29 Nov 2022 17:48:05 +0000 Message-ID: Date: Tue, 29 Nov 2022 18:48:05 +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 , Feng Tang Cc: 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 13:56, Marco Elver wrote: > On Tue, 29 Nov 2022 at 13:53, Feng Tang wrote: >> >> On Tue, Nov 29, 2022 at 08:02:51PM +0800, Vlastimil Babka wrote: >> > 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. >> >> I just quickly tried adding a new wrapper, like >> >> struct kmem_cache *debug_kmem_cache_create(const char *name, unsigned int size, >> unsigned int align, slab_flags_t flags, >> void (*ctor)(void *), slab_flags_t debug_flags); >> >> and found that, IIUC, both SLAB_KMALLOC and SLAB_NO_USER are creation >> time flag, while SLAB_SKIP_KFENCE is an allocation runtime flag which >> could be set after creation. >> >> So how about use the initial suggestion from Vlastimil to set the >> SKIP_KFENCE flag through an internal wrapper in slub_kunit.c? >> >> /* Only for debug and test use, to skip kfence allocation */ >> static inline void kmem_cache_skip_kfence(struct kmem_cache *s) >> { >> s->flags |= SLAB_SKIP_KFENCE; >> } > > Yes, that's fine - as long as it's local to slub_kunit.c, this seems > very reasonable. Wrapping just |= SLAB_SKIP_KFENCE won't help that much as you'd need to add a call to kmem_cache_skip_kfence() after each kmem_cache_create() in slub_kunit.c. That's why I propose a wrapper, *also internally defined in slub_kunit.c*, that calls kmem_cache_create() with flags |SLAB_NO_USER_FLAGS, then does s->flags |= SLAB_SKIP_KFENCE; then returns s. At this point said wrapper wouldn't even need align and ctor parameters and could pass 0 and NULL to kmem_cache_create() by itself, as no test uses different values. > Thanks, > -- Marco