From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f52.google.com (mail-pj1-f52.google.com [209.85.216.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 094582C17A0 for ; Wed, 8 Oct 2025 22:28:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.52 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759962507; cv=none; b=D/5UVoOrNGzBIcf8KQsYVwU1QI2na9ogrzhZrC5J/CHySOTSuFweCz+Y/yQvay4a3HuTJ0hPko/NNqHDD6X5BwfRIlYlYpQ24SbJ6dJRhfPiuKUJVcZ3s9ik681Nzf4nQ0KZDL/kNJXOnZq9GnmTQXDWGitM7VK5rxfsIUgxbp8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759962507; c=relaxed/simple; bh=cy6O3Pxt+g1sxlQ84A5B/3CkrY+2pljML5VEBIzZDjo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=BJ+E4Qv+OGnChQk587oqmf3/xJ32+W8tIfvdyzsx+kyWg70w7jEtsAdpNm+ionpzwuLv7xUJGxFHBjNzc31OD2lEQCDKEyh1mh+zWu3jOKEMNM9/9ikbsVwzNkHO6acWjrD7ophqPDc5LajUL8iv2teZnUK++jhPQ1iHLY0mbQI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kzalloc.com; spf=pass smtp.mailfrom=gmail.com; arc=none smtp.client-ip=209.85.216.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kzalloc.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-pj1-f52.google.com with SMTP id 98e67ed59e1d1-339a0b9ed6cso52390a91.3 for ; Wed, 08 Oct 2025 15:28:25 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1759962505; x=1760567305; h=content-transfer-encoding:in-reply-to:organization:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=m+FDQ7zQAPnlAXJ0xUMPhBN5Vu4l6pnGvG4mZcfsdHU=; b=B73/EeIVd+0z5CtrpuZGN8aLTKQ7zs7NjcHbLtrHiwz3R4ro63u2+1Pfgl0brR2GWs abyNcS8UCqhSOpt7E21PMkj77uA5OZ2UER7w62RSHW6MlmNcTFWaMDQI0+RW4OtxBI3o OYlswY1O+05K202071r9JJ1UP/Jboz9Vb9rESunLg8DAhUBVycrAIbkKUYRvdS8TUtLn 5RUEiSHVFN2m3BKoezA37skU7A81qc1cu2P8L4hocB6jOjlqcjUKbdNd858yZ4tfK+z2 ocfm8Q13T+wgBaUspi2NMTDp+k2543L82FlnujuMbxM8jwXxNToDBPQGQ4l6jwyEjuIZ eNKg== X-Forwarded-Encrypted: i=1; AJvYcCXtoP8Yk/LWB5w3yVJJkQkbOK0Rx8fpG/XrrWS08efe+mPrOR32UHZ2B5NpML5N8ZMUqqPqY+Re8WNaN30=@vger.kernel.org X-Gm-Message-State: AOJu0YxXTbz6+xT/6vYxa9W6uRCU/osfzTe5paxYpAYYVwm3+2UafgOe abvlAR1+52G19EAB55ks4HcXu+6bzsCpRckRWjKdh8KKvoOUEe/1OVjR X-Gm-Gg: ASbGncswy0N39g5YqZx6uT6kG6CnEC37HQv49nDE3NYTCeNRNhoqGHWBPsP0XDn2Gpi BAEVdESA6x7Ja0mBFvPb0nLQr5OFp9gvmPn1e6zmO3vmBlgcXLbOS7IIjQSiINL3qHUD/RdWa9w 3HkmYrbgMWdUC4owGjmnQcn0qJ7QuWs6sP1hGhev/0Qsu7IvszH0fsWy5I1jGKgryq08Xe6menp SwYnM2p6pellVlSY2DwwyJ0dSWU57SzJ9NMhIAdfL6/86DVQRoCKQj0xxYstM5/4r7BMHzHsm1c difKa7IGwcPv7VDwWSwGQm7NWhNw5zxIDCb3JP3CXA0z/RUWaipG9W5r0/Aisf+LoUQcht7p/RF /Zp1olYLFRVg0Cs1TZjXWJ80GjdyHm1g+ppxaTcz2ANoyRUxRptG265+GKM0Wni6Zzt4QVaE20B Td9WTY03EmpSLJv6BlAh7+mbRTBnOjOJ8HdabJ9PeFbg== X-Google-Smtp-Source: AGHT+IEdZv4j3V0V2ftmpYVdLCo1oL6MXTicZXNitpsrrWfaGVXXmpVpfjZcQG1gnntbQIiScsAVNQ== X-Received: by 2002:a05:6a20:12c4:b0:2c1:b47d:bcde with SMTP id adf61e73a8af0-32da80da615mr3884733637.1.1759962505124; Wed, 08 Oct 2025 15:28:25 -0700 (PDT) Received: from [192.168.50.136] ([118.32.98.101]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b62e3508744sm15811209a12.30.2025.10.08.15.28.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Oct 2025 15:28:24 -0700 (PDT) Message-ID: Date: Thu, 9 Oct 2025 07:28:19 +0900 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64: cpufeature: Don't cpu_enable_mte() when KASAN_GENERIC is active To: Andrey Konovalov Cc: Catalin Marinas , Will Deacon , James Morse , Yeoreum Yun , Vincenzo Frascino , Marc Zyngier , Mark Brown , Oliver Upton , Ard Biesheuvel , Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com References: <20251008210425.125021-3-ysk@kzalloc.com> Content-Language: en-US From: Yunseong Kim Organization: kzalloc In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Andrey, On 10/9/25 6:36 AM, Andrey Konovalov wrote: > On Wed, Oct 8, 2025 at 11:13 PM Yunseong Kim wrote: >> [...] > I do not understand this. Why is Generic KASAN incompatible with MTE? My board wouldn't boot on the debian debug kernel, so I enabled earlycon=pl011,0x40d0000 and checked via the UART console. > Running Generic KASAN in the kernel while having MTE enabled (and e.g. > used in userspace) seems like a valid combination. Then it must be caused by something else. Thank you for letting me know. It seems to be occurring in the call path as follows: cpu_enable_mte() -> try_page_mte_tagging(ZERO_PAGE(0)) -> VM_WARN_ON_ONCE(folio_test_hugetlb(page_folio(page))); https://elixir.bootlin.com/linux/v6.17/source/arch/arm64/include/asm/mte.h#L83 > The crash log above looks like a NULL-ptr-deref. On which line of code > does it happen? Decoded stack trace here: [ 0.000000] Unable to handle kernel paging request at virtual address dfff800000000005 [ 0.000000] KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] [ 0.000000] Mem abort info: [ 0.000000] ESR = 0x0000000096000005 [ 0.000000] EC = 0x25: DABT (current EL), IL = 32 bits [ 0.000000] SET = 0, FnV = 0 [ 0.000000] EA = 0, S1PTW = 0 [ 0.000000] FSC = 0x05: level 1 translation fault [ 0.000000] Data abort info: [ 0.000000] ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 [ 0.000000] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 [ 0.000000] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [ 0.000000] [dfff800000000005] address between user and kernel address ranges [ 0.000000] Internal error: Oops: 0000000096000005 [#1] SMP [ 0.000000] Modules linked in: [ 0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.17+unreleased-debug-arm64 #1 PREEMPTLAZY Debian 6.17-1~exp1 [ 0.000000] pstate: 800000c9 (Nzcv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 0.000000] pc : cpu_enable_mte (debian/build/build_arm64_none_debug-arm64/include/linux/page-flags.h:1065 (discriminator 1) debian/build/build_arm64_none_debug-arm64/arch/arm64/include/asm/mte.h:83 (discriminator 1) debian/build/build_arm64_none_debug-arm64/arch/arm64/kernel/cpufeature.c:2419 (discriminator 1)) [ 0.000000] lr : cpu_enable_mte (debian/build/build_arm64_none_debug-arm64/include/linux/page-flags.h:1065 (discriminator 1) debian/build/build_arm64_none_debug-arm64/arch/arm64/include/asm/mte.h:83 (discriminator 1) debian/build/build_arm64_none_debug-arm64/arch/arm64/kernel/cpufeature.c:2419 (discriminator 1)) [ 0.000000] sp : ffff800084f67d80 [ 0.000000] x29: ffff800084f67d80 x28: 0000000000000043 x27: 0000000000000001 [ 0.000000] x26: 0000000000000001 x25: ffff800084204008 x24: ffff800084203da8 [ 0.000000] x23: ffff800084204000 x22: ffff800084203000 x21: ffff8000865a8000 [ 0.000000] x20: fffffffffffffffe x19: fffffdffddaa6a00 x18: 0000000000000011 [ 0.000000] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 [ 0.000000] x14: 0000000000000000 x13: 0000000000000001 x12: ffff700010a04829 [ 0.000000] x11: 1ffff00010a04828 x10: ffff700010a04828 x9 : dfff800000000000 [ 0.000000] x8 : ffff800085024143 x7 : 0000000000000001 x6 : ffff700010a04828 [ 0.000000] x5 : ffff800084f9d200 x4 : 0000000000000000 x3 : ffff8000800794ac [ 0.000000] x2 : 0000000000000005 x1 : dfff800000000000 x0 : 000000000000002e [ 0.000000] Call trace: [ 0.000000] cpu_enable_mte (debian/build/build_arm64_none_debug-arm64/√ (discriminator 1) debian/build/build_arm64_none_debug-arm64/arch/arm64/include/asm/mte.h:83 (discriminator 1) debian/build/build_arm64_none_debug-arm64/arch/arm64/kernel/cpufeature.c:2419 (discriminator 1)) (P) [ 0.000000] enable_cpu_capabilities (debian/build/build_arm64_none_debug-arm64/arch/arm64/kernel/cpufeature.c:3561 (discriminator 2)) [ 0.000000] setup_boot_cpu_features (debian/build/build_arm64_none_debug-arm64/arch/arm64/kernel/cpufeature.c:3888 debian/build/build_arm64_none_debug-arm64/arch/arm64/kernel/cpufeature.c:3906) [ 0.000000] smp_prepare_boot_cpu (debian/build/build_arm64_none_debug-arm64/arch/arm64/kernel/smp.c:466) [ 0.000000] start_kernel (debian/build/build_arm64_none_debug-arm64/init/main.c:929) [ 0.000000] __primary_switched (debian/build/build_arm64_none_debug-arm64/arch/arm64/kernel/head.S:247) [ 0.000000] Code: 9100c280 d2d00001 f2fbffe1 d343fc02 (38e16841) All code ======== 0: 9100c280 add x0, x20, #0x30 4: d2d00001 mov x1, #0x800000000000 // #140737488355328 8: f2fbffe1 movk x1, #0xdfff, lsl #48 c: d343fc02 lsr x2, x0, #3 10:* 38e16841 ldrsb w1, [x2, x1] <-- trapping instruction Code starting with the faulting instruction =========================================== 0: 38e16841 ldrsb w1, [x2, x1] [ 0.000000] ---[ end trace 0000000000000000 ]--- [ 0.000000] Kernel panic - not syncing: Attempted to kill the idle task! [ 0.000000] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]--- If there are any other points you'd like me to check or directions, please let me know. Thank you! Yunseong