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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0EFE3C433EF for ; Tue, 12 Jul 2022 15:13:47 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 685B794009B; Tue, 12 Jul 2022 11:13:47 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 635B5940063; Tue, 12 Jul 2022 11:13:47 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4FCE794009B; Tue, 12 Jul 2022 11:13:47 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 40DB0940063 for ; Tue, 12 Jul 2022 11:13:47 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 1487E20BD1 for ; Tue, 12 Jul 2022 15:13:47 +0000 (UTC) X-FDA: 79678792494.13.9EA09E2 Received: from gentwo.de (gentwo.de [161.97.139.209]) by imf21.hostedemail.com (Postfix) with ESMTP id 4E0461C006E for ; Tue, 12 Jul 2022 15:13:46 +0000 (UTC) Received: by gentwo.de (Postfix, from userid 1001) id B8AE0B00422; Tue, 12 Jul 2022 17:13:44 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gentwo.de; s=default; t=1657638824; bh=7+H5sOVkN3QxHU6DQU93Nr8Rzf1W/u/tyJLdV84maC4=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=Xj/GN/J6jJvlJrzAyTYFvqxapzZWR96npANp8WILastYr1yA6AZofEFMiv0vdCtXD geCh8MPf7MLjcbnU0dWUgWYTBhC6kBakj1/XnLfI9qT0E6AiiU8tr4VHGIQ5GmvxRg t+F/h14WJW+QqpvD7NiLVNcqK6RBEO8F8yLCdYu8sGJnNhgP7MoPFqvZRfm7TZI8o4 oxSJJ3eHrQa+oK2MHqcybzm3eIZ83WTdJaTro0WTbw+lSPpl59S0L4l0CW1EcfdPrU aPa4aRoXX985c/dKImmvDelc80KgvwmYtjuB/hfMb0gzBaxtfk6xl5UuuP4d0bVsCJ 3CMrv8AUiZ+8A== Received: from localhost (localhost [127.0.0.1]) by gentwo.de (Postfix) with ESMTP id B7EBEB0026E; Tue, 12 Jul 2022 17:13:44 +0200 (CEST) Date: Tue, 12 Jul 2022 17:13:44 +0200 (CEST) From: Christoph Lameter To: Hyeonggon Yoo <42.hyeyoo@gmail.com> cc: Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Vlastimil Babka , Roman Gushchin , Joe Perches , Vasily Averin , Matthew WilCox , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 16/16] mm/sl[au]b: check if large object is valid in __ksize() In-Reply-To: <20220712133946.307181-17-42.hyeyoo@gmail.com> Message-ID: References: <20220712133946.307181-1-42.hyeyoo@gmail.com> <20220712133946.307181-17-42.hyeyoo@gmail.com> User-Agent: Alpine 2.22 (DEB 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1657638826; a=rsa-sha256; cv=none; b=2FMFMbgi/ycZU1RClGkxz8CTMH0iCgPsfiL54OE202/8pQDC6GTcZedPKHJaV8qvb+Nshu uwvkLTTkHMhtyEzmAJyjOIimvMcA+zIfpsDyEPlgtfAS3WO8ZJ+HonDHGh8hkdbs5pwk+W UPC2+8seCziUk0rW63rTTcrQ/q+3LuI= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=gentwo.de header.s=default header.b="Xj/GN/J6"; dmarc=pass (policy=none) header.from=gentwo.de; spf=pass (imf21.hostedemail.com: domain of cl@gentwo.de designates 161.97.139.209 as permitted sender) smtp.mailfrom=cl@gentwo.de ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1657638826; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=qfeMTdLRpBSxU4Hu6dNMkTOU1oQkYZnE3ARvzgVICDA=; b=S+XiUq4x2ZkxvHMBD8VGpMryU9AQnK0FKrdgZnDIrRKkwGFXA2TS8zPZoOg+zX8OzEt2l6 XLWk08m8bBlRmfgA9yxqtsA3yI2FF9DMuG9D4TR65nxvRouviLFPhLE4VxVBNTN6w54j8H gzY9kHXzezV6KgJC1z6bJcOWeIlLPAw= X-Stat-Signature: d4y5p4j38eh3g6nw54p6b4fercn3368h X-Rspamd-Queue-Id: 4E0461C006E Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=gentwo.de header.s=default header.b="Xj/GN/J6"; dmarc=pass (policy=none) header.from=gentwo.de; spf=pass (imf21.hostedemail.com: domain of cl@gentwo.de designates 161.97.139.209 as permitted sender) smtp.mailfrom=cl@gentwo.de X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1657638826-53692 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: On Tue, 12 Jul 2022, Hyeonggon Yoo wrote: > __ksize() returns size of objects allocated from slab allocator. > When invalid object is passed to __ksize(), returning zero > prevents further memory corruption and makes caller be able to > check if there is an error. > > If address of large object is not beginning of folio or size of > the folio is too small, it must be invalid. Return zero in such cases. Why return 0 if there is an error and why bother the callers with these checks. BUG()? > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 1f8db7959366..0d6cbe9d7ad0 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -1013,8 +1013,12 @@ size_t __ksize(const void *object) > > folio = virt_to_folio(object); > > - if (unlikely(!folio_test_slab(folio))) > + if (unlikely(!folio_test_slab(folio))) { > + if (WARN_ON(object != folio_address(folio) || > + folio_size(folio) <= KMALLOC_MAX_CACHE_SIZE)) Hmmm... This may change things a bit. Before this patch it was possible to determine the storage size of order-0 pages using ksize(). Now this returns 0? I guess this is an error since the order-0 page cannot come from slab allocations.