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 EE8A7C43217 for ; Wed, 9 Nov 2022 11:17:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229899AbiKILRC (ORCPT ); Wed, 9 Nov 2022 06:17:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59074 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230294AbiKILQb (ORCPT ); Wed, 9 Nov 2022 06:16:31 -0500 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B9C672AC7D for ; Wed, 9 Nov 2022 03:16:11 -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 5E8F41F6E6; Wed, 9 Nov 2022 11:16:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1667992570; 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=nt/ta1l555vr4EsYp1C+UKFBUJaf1xMeh2se9hvTXV4=; b=A+ZNMvKzJsRbs3XX0kDqucBV1QNYQeSVip1ZSRDe6o/ioxjNewKigBfJ/jKiAwRYHN8oOY tfDdGmNMDy0YWSd/Q0hEmo8HW2llBqZasFgJQ+Qc077dyXpHhVfAvbnhHEY8ddylWvpNuY p0/5Tjy2pNTIKp0I22D9cw+9UUKMJaY= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1667992570; 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=nt/ta1l555vr4EsYp1C+UKFBUJaf1xMeh2se9hvTXV4=; b=v+hsFIFU7SeXH0BVMt0N5U6cmbClwvje2b0/4Xit0/rOiAaD5EWurfl9KA9zqMrvmbtZrT jeTJiqAygmEW+6Bw== 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 33ACA1331F; Wed, 9 Nov 2022 11:16:10 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id R5NDC/qLa2M7NAAAMHmgww (envelope-from ); Wed, 09 Nov 2022 11:16:10 +0000 Message-ID: Date: Wed, 9 Nov 2022 12:16:09 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.1 Subject: Re: [PATCH v2 0/3] Refactor __kmem_cache_create() and fix memory leak Content-Language: en-US To: Hyeonggon Yoo <42.hyeyoo@gmail.com>, Liu Shixin Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Rasmus Villemoes References: <20221031134747.3049593-1-liushixin2@huawei.com> 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 11/3/22 14:23, Hyeonggon Yoo wrote: > On Wed, Nov 02, 2022 at 04:53:08PM +0800, Liu Shixin wrote: >> On 2022/11/2 15:46, Hyeonggon Yoo wrote: >> > On Mon, Oct 31, 2022 at 09:47:44PM +0800, Liu Shixin wrote: >> >> I found a memory leak of kobj->name in sysfs_slab_add() which is introduced >> >> by 80da026a8e5d ("mm/slub: fix slab double-free in case of duplicate sysfs filename"). >> >> Following the rules stated in the comment for kobject_init_and_add(): >> > Thank you for reporting this! Indeed it seems tried to fix double free but >> > introduced a leak. >> > >> >> If this function returns an error, kobject_put() must be called to >> >> properly clean up the memory associated with the object. >> >> >> >> We should use kobject_put() to free kobject. >> > But what to do if a cache is created early and later sysfs_slab_add() failed? >> > (Which is unlikely on normal condition) >> > >> > With this series it introduces use-after-free if sysfs_slab_add() in >> > slab_sysfs_init() failed. Should we just call BUG() or something like that? >> >> Thanks for your discovery, what I missed. > > You're welcome. > >> I prefer to panic directly, just as create_boot_cache() does. > > IMHO that should be nothing serious. but let's hear maintainers' opinion. > >> Of couse, if you want the system to continue booting, I think it's possible to distinguish them >> by slab_state. > > I'm afraid to make it more complex :( +Cc Rasmus who did a recent patch in this area. Thread starts here: https://lore.kernel.org/all/20221031134747.3049593-1-liushixin2@huawei.com/ As for me, I don't think we should be addung new BUG() or panic() in general, and especially not for a failing sysfs add. AFAICS create_boot_cache() might panic, but not because of sysfs, as that's delayed until slab_sysfs_init() and we don't panic anymore in the latter. So yeah, it could work to tell sysfs_slab_add() whether it should not do the kobject_put() as it's a boot cache. The slab_state should work. > >> Looking forward to your advice. >> Thanks, >> > >> >> But we can't simply add kobject_put() since it will free kmem_cache too. >> >> If we use kobject_put(), we need to skip other release functions. >> >> >> >> In this series, We refactor the code to separate sysfs_slab_add() and >> >> debugfs_slab_add() from __kmem_cache_create(), and then use kobject_put() >> >> to free kobject in sysfs_slab_add(). This can fix the memory leak of >> >> kobject->name. >> >> >> >> v1->v2: Fix build error reported by kernel test robot . >> >> >> >> Liu Shixin (3): >> >> mm/slab_common: Move cache_name to create_cache() >> >> mm/slub: Refactor __kmem_cache_create() >> >> mm/slub: Fix memory leak of kobj->name in sysfs_slab_add() >> >> >> >> include/linux/slub_def.h | 11 +++++++++ >> >> mm/slab_common.c | 44 ++++++++++++++++++---------------- >> >> mm/slub.c | 52 ++++++++++------------------------------ >> >> 3 files changed, 48 insertions(+), 59 deletions(-) >> >> >> >> -- >> >> 2.25.1 >> >> >> >