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 458AFC433F5 for ; Mon, 30 May 2022 15:46:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242691AbiE3Pqp (ORCPT ); Mon, 30 May 2022 11:46:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57680 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242246AbiE3PqX (ORCPT ); Mon, 30 May 2022 11:46:23 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BBC60A26C3 for ; Mon, 30 May 2022 07:57:08 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 1204FB80D84 for ; Mon, 30 May 2022 14:57:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30034C385B8; Mon, 30 May 2022 14:57:03 +0000 (UTC) Date: Mon, 30 May 2022 15:56:59 +0100 From: Catalin Marinas To: Patrick Wang Cc: Yee Lee , linux-kernel@vger.kernel.org, Kuan-Ying.lee@mediatek.com, Andrew.Yang@mediatek.com, Sunny.Kao@mediatek.com, chinwen.chang@mediatek.com, Andrew Morton , Matthias Brugger , "open list:MEMORY MANAGEMENT" , "moderated list:ARM/Mediatek SoC support" , "moderated list:ARM/Mediatek SoC support" , Ariel Marcovitch Subject: Re: [PATCH] mm: kmemleak: Skip check in kmemleak_*_phys when pfn bound is not ready Message-ID: References: <20220527032504.30341-1-yee.lee@mediatek.com> <05cfaf936a0c5f37f2e7ba779a8a1b0a6252be96.camel@mediatek.com> <64281aab-0301-7237-d72c-b7ab41bf50e4@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <64281aab-0301-7237-d72c-b7ab41bf50e4@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Patrick, On Mon, May 30, 2022 at 09:32:18PM +0800, Patrick Wang wrote: > On 2022/5/30 10:27, Yee Lee wrote: > > On Fri, 2022-05-27 at 21:39 +0800, patrick wang wrote: > > > On Fri, May 27, 2022 at 11:25 AM wrote: > > > > From: Yee Lee > > > > > > > > In some archs (arm64), memblock allocates memory in boot time when > > > > the pfn boundary (max_pfn/min_pfn) is not ready. The lowmen checks in > > > > kmemleak_*_phys() drop those blocks and cause some false leak alarms > > > > on common kernel objects. > > > > > > > > Kmemleak output: (Qemu/arm64) > > > > unreferenced object 0xffff0000c0170a00 (size 128): > > > > comm "swapper/0", pid 1, jiffies 4294892404 (age 126.208s) > > > > hex dump (first 32 bytes): > > > > 62 61 73 65 00 00 00 00 00 00 00 00 00 00 00 00 base............ > > > > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > > > > backtrace: > > > > [<(____ptrval____)>] __kmalloc_track_caller+0x1b0/0x2e4 > > > > [<(____ptrval____)>] kstrdup_const+0x8c/0xc4 > > > > [<(____ptrval____)>] kvasprintf_const+0xbc/0xec > > > > [<(____ptrval____)>] kobject_set_name_vargs+0x58/0xe4 > > > > [<(____ptrval____)>] kobject_add+0x84/0x100 > > > > [<(____ptrval____)>] __of_attach_node_sysfs+0x78/0xec > > > > [<(____ptrval____)>] of_core_init+0x68/0x104 > > > > [<(____ptrval____)>] driver_init+0x28/0x48 > > > > [<(____ptrval____)>] do_basic_setup+0x14/0x28 > > > > [<(____ptrval____)>] kernel_init_freeable+0x110/0x178 > > > > [<(____ptrval____)>] kernel_init+0x20/0x1a0 > > > > [<(____ptrval____)>] ret_from_fork+0x10/0x20 > > > > > > > > This patch relaxs the boundary checking in kmemleak_*_phys api > > > > if max_low_pfn is uninitialzed. > > > > > > > > Fixes: 23c2d4 (mm: kmemleak: take a full lowmem check in kmemleak_*_phy) BTW, please use at least 12 characters for the git sha1, the above is ambiguous. > > > > Signed-off-by: Yee Lee > > > > --- > > > > mm/kmemleak.c | 8 ++++---- > > > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/mm/kmemleak.c b/mm/kmemleak.c > > > > index a182f5ddaf68..6b2af544aa0f 100644 > > > > --- a/mm/kmemleak.c > > > > +++ b/mm/kmemleak.c > > > > @@ -1132,7 +1132,7 @@ EXPORT_SYMBOL(kmemleak_no_scan); > > > > void __ref kmemleak_alloc_phys(phys_addr_t phys, size_t size, int min_count, > > > > gfp_t gfp) > > > > { > > > > - if (PHYS_PFN(phys) >= min_low_pfn && PHYS_PFN(phys) < max_low_pfn) > > > > + if (!max_low_pfn || (PHYS_PFN(phys) >= min_low_pfn && PHYS_PFN(phys) < max_low_pfn)) > > > > > > Just skip checking will bring the crash possibility back. Seems > > > it's beyond these interfaces' handle scope for this situation, > > > since "min_low_pfn" and "max_low_pfn" are depending on arches. > > > > Yes, for the cases beyond the pfn guard, users have to take care the > > boundary by themselves. > > Could we record these early calling and deal with them when it's > ready? Is this appropriate? > > I have an implementation based on this approach. Could you please > help to have a test on your machine as well? And someone to take > a look or review? We had something similar until 5.4, removed by commit c5665868183f ("mm: kmemleak: use the memory pool for early allocations"). It was a bit painful as we never had the right buffer, so I'm not keen on adding it back. > From 82cae75dfaa78f414faf85bb49133e95159c041a Mon Sep 17 00:00:00 2001 > From: Patrick Wang > Date: Mon, 30 May 2022 18:38:23 +0800 > Subject: [PATCH] mm: kmemleak: record early operations and handle later > > The kmemleak_*_phys() interface uses "min_low_pfn" and > "max_low_pfn" to check address. But on some architectures, > kmemleak_*_phys() is called before those two variables > initialized. Record these early operations and handle them > when kmemleak_*_phys() are ready. Could we instead record everything (no checks) but later avoid scanning if below min or above max_low_pfn? We can add an OBJECT_PHYS flag to all objects allocated via kmemleak_*_phys() and always check the virt_to_phys() boundaries at scan time. It may actually help with this problem as well: https://lore.kernel.org/r/9dd08bb5-f39e-53d8-f88d-bec598a08c93@gmail.com -- Catalin