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 6BA70C61D97 for ; Thu, 26 Jan 2023 23:34:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232793AbjAZXeb (ORCPT ); Thu, 26 Jan 2023 18:34:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45140 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229498AbjAZXe3 (ORCPT ); Thu, 26 Jan 2023 18:34:29 -0500 Received: from mail-pf1-x433.google.com (mail-pf1-x433.google.com [IPv6:2607:f8b0:4864:20::433]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6FB566E8D for ; Thu, 26 Jan 2023 15:34:28 -0800 (PST) Received: by mail-pf1-x433.google.com with SMTP id z31so2201880pfw.4 for ; Thu, 26 Jan 2023 15:34:28 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=ZmlCUBRCPwLvDMyRKhmvFFYyCxvm8e49EMH29s2svEk=; b=V7pzD6PvMlRTA677LV794Nzyy1S2TBgILbVqqW6ty0pWMAGXaCr9JdjcF4So27okbd lVit+lRnXs05quAU4kmV8NadesAnDUqUDnKSSRv8uFKBvl13EWRY/3jwA4NIc4SW7E1/ wbN4UZGtuSLt5Tqu2/oDsQQGyxZzgoV3/g+iG6eGqjhkyCfL1dbMzl3YF0C4+06VhNQq 5gq77m4p+7PHXo3V7i5gNUiYcoBov8NDX2ksttB2+xDdKxOj68e0hFOm4zscS7mzILyi /u7b+RecsNMfrR7+jZqk/9L6hBllhwQCV4deoye22sdy6UXWaMV3B65O+2zMckYRV+6v WVgQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=ZmlCUBRCPwLvDMyRKhmvFFYyCxvm8e49EMH29s2svEk=; b=BAt7IdLLpLOUiYwG6NgayhvVfi3IlrPuD4DZsIfNPjKESP8g6tllzrzlcnqzJDHMCC 6rSrlwmCLqbf0YZafHxOfLVg0JQPXjjcr+rdnkg+xk+wDlL6PRzzjyEJKjkvaxKIwGw7 oKBchbVa3eJyOS6xVKd7eFdHm2MysiCLSAchbv4IYa0mHlatHMQMtpe/DhNwpf1ku16b cAOr/IZ44AoIZp4VGH0IhprI0E5gRfPrtNuSK7CiO55n1cjGPMAvgwC5wgPil3plqNW4 iU+bOytMGI89I1FLM80yjb4aXOxxuYqX8usNU/tcEZmE21qBDsAdxO+iRhjsX27N0DEH w5eA== X-Gm-Message-State: AO0yUKVU8g7whqIHspGCmx+xQ4hj7zaCo4/d76czo7fDengj4oL2iZjp FcbA2APa2pWr5TXtFgpamSL5yeDaQEy41Tpc84U= X-Google-Smtp-Source: AK7set+jurZu+DhTB98Wjvu0Zv3kgBKXskjxfUjFlfo8kCzK0PCeGHCM1YBpxMKkAjD/DohwQdb1WzQR6i+wH7KREwg= X-Received: by 2002:a05:6a00:23c2:b0:592:5653:facb with SMTP id g2-20020a056a0023c200b005925653facbmr365495pfc.28.1674776067755; Thu, 26 Jan 2023 15:34:27 -0800 (PST) MIME-Version: 1.0 References: <150768c55722311699fdcf8f5379e8256749f47d.1674716617.git.christophe.leroy@csgroup.eu> In-Reply-To: <150768c55722311699fdcf8f5379e8256749f47d.1674716617.git.christophe.leroy@csgroup.eu> From: Andrey Konovalov Date: Fri, 27 Jan 2023 00:34:16 +0100 Message-ID: Subject: Re: [PATCH] kasan: Fix Oops due to missing calls to kasan_arch_is_ready() To: Christophe Leroy Cc: Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Vincenzo Frascino , Andrew Morton , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, kasan-dev@googlegroups.com, Nathan Lynch , Michael Ellerman Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 26, 2023 at 8:08 AM Christophe Leroy wrote: > > On powerpc64, you can build a kernel with KASAN as soon as you build it > with RADIX MMU support. However if the CPU doesn't have RADIX MMU, > KASAN isn't enabled at init and the following Oops is encountered. > > [ 0.000000][ T0] KASAN not enabled as it requires radix! > > [ 4.484295][ T26] BUG: Unable to handle kernel data access at 0xc00e000000804a04 > [ 4.485270][ T26] Faulting instruction address: 0xc00000000062ec6c > [ 4.485748][ T26] Oops: Kernel access of bad area, sig: 11 [#1] > [ 4.485920][ T26] BE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries > [ 4.486259][ T26] Modules linked in: > [ 4.486637][ T26] CPU: 0 PID: 26 Comm: kworker/u2:2 Not tainted 6.2.0-rc3-02590-gf8a023b0a805 #249 > [ 4.486907][ T26] Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1200 0xf000005 of:SLOF,HEAD pSeries > [ 4.487445][ T26] Workqueue: eval_map_wq .tracer_init_tracefs_work_func > [ 4.488744][ T26] NIP: c00000000062ec6c LR: c00000000062bb84 CTR: c0000000002ebcd0 > [ 4.488867][ T26] REGS: c0000000049175c0 TRAP: 0380 Not tainted (6.2.0-rc3-02590-gf8a023b0a805) > [ 4.489028][ T26] MSR: 8000000002009032 CR: 44002808 XER: 00000000 > [ 4.489584][ T26] CFAR: c00000000062bb80 IRQMASK: 0 > [ 4.489584][ T26] GPR00: c0000000005624d4 c000000004917860 c000000001cfc000 1800000000804a04 > [ 4.489584][ T26] GPR04: c0000000003a2650 0000000000000cc0 c00000000000d3d8 c00000000000d3d8 > [ 4.489584][ T26] GPR08: c0000000049175b0 a80e000000000000 0000000000000000 0000000017d78400 > [ 4.489584][ T26] GPR12: 0000000044002204 c000000003790000 c00000000435003c c0000000043f1c40 > [ 4.489584][ T26] GPR16: c0000000043f1c68 c0000000043501a0 c000000002106138 c0000000043f1c08 > [ 4.489584][ T26] GPR20: c0000000043f1c10 c0000000043f1c20 c000000004146c40 c000000002fdb7f8 > [ 4.489584][ T26] GPR24: c000000002fdb834 c000000003685e00 c000000004025030 c000000003522e90 > [ 4.489584][ T26] GPR28: 0000000000000cc0 c0000000003a2650 c000000004025020 c000000004025020 > [ 4.491201][ T26] NIP [c00000000062ec6c] .kasan_byte_accessible+0xc/0x20 > [ 4.491430][ T26] LR [c00000000062bb84] .__kasan_check_byte+0x24/0x90 > [ 4.491767][ T26] Call Trace: > [ 4.491941][ T26] [c000000004917860] [c00000000062ae70] .__kasan_kmalloc+0xc0/0x110 (unreliable) > [ 4.492270][ T26] [c0000000049178f0] [c0000000005624d4] .krealloc+0x54/0x1c0 > [ 4.492453][ T26] [c000000004917990] [c0000000003a2650] .create_trace_option_files+0x280/0x530 > [ 4.492613][ T26] [c000000004917a90] [c000000002050d90] .tracer_init_tracefs_work_func+0x274/0x2c0 > [ 4.492771][ T26] [c000000004917b40] [c0000000001f9948] .process_one_work+0x578/0x9f0 > [ 4.492927][ T26] [c000000004917c30] [c0000000001f9ebc] .worker_thread+0xfc/0x950 > [ 4.493084][ T26] [c000000004917d60] [c00000000020be84] .kthread+0x1a4/0x1b0 > [ 4.493232][ T26] [c000000004917e10] [c00000000000d3d8] .ret_from_kernel_thread+0x58/0x60 > [ 4.495642][ T26] Code: 60000000 7cc802a6 38a00000 4bfffc78 60000000 7cc802a6 38a00001 4bfffc68 60000000 3d20a80e 7863e8c2 792907c6 <7c6348ae> 20630007 78630fe0 68630001 > [ 4.496704][ T26] ---[ end trace 0000000000000000 ]--- > > The Oops is due to kasan_byte_accessible() not checking the readiness > of KASAN. Add missing call to kasan_arch_is_ready() and bail out when > not ready. The same problem is observed with ____kasan_kfree_large() > so fix it the same. > > Also, as KASAN is not available and no shadow area is allocated for > linear memory mapping, there is no point in allocating shadow mem for > vmalloc memory as shown below in /sys/kernel/debug/kernel_page_tables > > ---[ kasan shadow mem start ]--- > 0xc00f000000000000-0xc00f00000006ffff 0x00000000040f0000 448K r w pte valid present dirty accessed > 0xc00f000000860000-0xc00f00000086ffff 0x000000000ac10000 64K r w pte valid present dirty accessed > 0xc00f3ffffffe0000-0xc00f3fffffffffff 0x0000000004d10000 128K r w pte valid present dirty accessed > ---[ kasan shadow mem end ]--- > > So, also verify KASAN readiness before allocating and poisoning > shadow mem for VMAs. Hi Cristophe, Would it possible to unify kasan_arch_is_ready with the already existing kasan_enabled check? Both functions seem to be serving a similar purpose: for example this patch adds kasan_arch_is_ready into __kasan_poison_vmalloc, which is called by kasan_poison_vmalloc when kasan_enabled returns true. The kasan_enabled is only implemented for HW_TAGS right now, but it should be easy enough to make it work other cases by kasan_flag_enabled into common.c and adding __wrappers for shadow-related functions into include/linux/kasan.h. This way architectures won't need to define their own static key and duplicate the functionality. I don't mind having this patch applied as is, considering that it's a fix. However, if the unification that I mentioned is possible, that would be a nice improvement. Thanks!