From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.9]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3F7313563F6; Thu, 18 Jun 2026 18:12:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.9 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781806334; cv=none; b=kGp6anikA9U7HFgUj+sxvniTmZWob0oVXKNtTW1dC2/QcnkpWDl1IiVw/KCmfxHo1HT4ae5c9PdNoCf5N7RDs47j6dukHmodWeyjma1JkbGZH6PZoZN8fRVaTt0JoFhfYq9Nqwug/XynUrsiV22ewQEUJbdzyDhMO5wzn6tTKFk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781806334; c=relaxed/simple; bh=KiOrftyVXSm2xYANpVQq31qn6xeMhRpGmJFyi1EtirQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Ty56tOau78DxSGjT4S3hSb9BpupQGyWF/nP7X8d1p4l1JNHJCICIlwhcr9MBbfl00jGC7QlegTHNbwheDcqDURk/6P2GofcBP78pgk3QIriKhbvPwb6zzLjP/dhNlIbGCKBim8dRESLbDpvND6C8kPoBjFfdL8BTBJi5lByH2Yg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=j5d3vJE0; arc=none smtp.client-ip=192.198.163.9 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="j5d3vJE0" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1781806332; x=1813342332; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=KiOrftyVXSm2xYANpVQq31qn6xeMhRpGmJFyi1EtirQ=; b=j5d3vJE0wzeOcr+p7IdCLNGMxxJsgxM+pCU/PWGOPwWM06xOxw48hICF LQQr7MpgbFVOrPUgyvvcWZuCBoYF/PBU00mexR193Bn3vfHcWipqwM8v5 f8Q0XAG517OdSxN/LqjlVYDDgjBcowTribeFU1MqMrN+i/464I4vPRQV/ lpD0+5Dm5zIUD2dAYQrKLZm6Swu5YZajYg7IOdqOqFes/3s+KA5M+tdo5 lYCEkM7nCQSLnClUG3kdCDJ9XBlQlHRAAkq4OtXrf1zxURy3O3C1vasue D2LWYo2hZ3eRJS20GD53kd7Dlmpn0DPHTueS3Zmv6d7lgWa7i8nWsgf0z w==; X-CSE-ConnectionGUID: jncuIO91RaeN0+BdsG541Q== X-CSE-MsgGUID: /aUGj6DpQ4OVE7bGShr17g== X-IronPort-AV: E=McAfee;i="6800,10657,11821"; a="93301991" X-IronPort-AV: E=Sophos;i="6.24,211,1774335600"; d="scan'208";a="93301991" Received: from fmviesa002.fm.intel.com ([10.60.135.142]) by fmvoesa103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jun 2026 11:12:11 -0700 X-CSE-ConnectionGUID: EEHx02poQu2Do1OLp+UeRQ== X-CSE-MsgGUID: 8x0vdmXVRXmypy68vhLGgg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.24,211,1774335600"; d="scan'208";a="272130460" Received: from rfrazer-mobl3.amr.corp.intel.com (HELO [10.125.111.222]) ([10.125.111.222]) by fmviesa002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jun 2026 11:12:10 -0700 Message-ID: <3207a706-354c-4e9d-ba53-dded1abb1842@intel.com> Date: Thu, 18 Jun 2026 11:12:09 -0700 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 v1] kasan: Fix false-positive wild-memory-access on x86 under 5-level paging To: Borislav Petkov , Ihor Solodrai Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Eduard Zingerman , Kumar Kartikeya Dwivedi , Andrey Ryabinin , Andrew Morton , bpf@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Andrey Konovalov References: <20260610175651.647515-1-ihor.solodrai@linux.dev> <326b85af-c41a-4387-90a0-60720111934d@linux.dev> <20260618170913.GBajQmOQyOiBLqopUl@fat_crate.local> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; keydata= xsFNBE6HMP0BEADIMA3XYkQfF3dwHlj58Yjsc4E5y5G67cfbt8dvaUq2fx1lR0K9h1bOI6fC oAiUXvGAOxPDsB/P6UEOISPpLl5IuYsSwAeZGkdQ5g6m1xq7AlDJQZddhr/1DC/nMVa/2BoY 2UnKuZuSBu7lgOE193+7Uks3416N2hTkyKUSNkduyoZ9F5twiBhxPJwPtn/wnch6n5RsoXsb ygOEDxLEsSk/7eyFycjE+btUtAWZtx+HseyaGfqkZK0Z9bT1lsaHecmB203xShwCPT49Blxz VOab8668QpaEOdLGhtvrVYVK7x4skyT3nGWcgDCl5/Vp3TWA4K+IofwvXzX2ON/Mj7aQwf5W iC+3nWC7q0uxKwwsddJ0Nu+dpA/UORQWa1NiAftEoSpk5+nUUi0WE+5DRm0H+TXKBWMGNCFn c6+EKg5zQaa8KqymHcOrSXNPmzJuXvDQ8uj2J8XuzCZfK4uy1+YdIr0yyEMI7mdh4KX50LO1 pmowEqDh7dLShTOif/7UtQYrzYq9cPnjU2ZW4qd5Qz2joSGTG9eCXLz5PRe5SqHxv6ljk8mb ApNuY7bOXO/A7T2j5RwXIlcmssqIjBcxsRRoIbpCwWWGjkYjzYCjgsNFL6rt4OL11OUF37wL QcTl7fbCGv53KfKPdYD5hcbguLKi/aCccJK18ZwNjFhqr4MliQARAQABzUVEYXZpZCBDaHJp c3RvcGhlciBIYW5zZW4gKEludGVsIFdvcmsgQWRkcmVzcykgPGRhdmUuaGFuc2VuQGludGVs LmNvbT7CwXgEEwECACIFAlQ+9J0CGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEGg1 lTBwyZKwLZUP/0dnbhDc229u2u6WtK1s1cSd9WsflGXGagkR6liJ4um3XCfYWDHvIdkHYC1t MNcVHFBwmQkawxsYvgO8kXT3SaFZe4ISfB4K4CL2qp4JO+nJdlFUbZI7cz/Td9z8nHjMcWYF IQuTsWOLs/LBMTs+ANumibtw6UkiGVD3dfHJAOPNApjVr+M0P/lVmTeP8w0uVcd2syiaU5jB aht9CYATn+ytFGWZnBEEQFnqcibIaOrmoBLu2b3fKJEd8Jp7NHDSIdrvrMjYynmc6sZKUqH2 I1qOevaa8jUg7wlLJAWGfIqnu85kkqrVOkbNbk4TPub7VOqA6qG5GCNEIv6ZY7HLYd/vAkVY E8Plzq/NwLAuOWxvGrOl7OPuwVeR4hBDfcrNb990MFPpjGgACzAZyjdmYoMu8j3/MAEW4P0z F5+EYJAOZ+z212y1pchNNauehORXgjrNKsZwxwKpPY9qb84E3O9KYpwfATsqOoQ6tTgr+1BR CCwP712H+E9U5HJ0iibN/CDZFVPL1bRerHziuwuQuvE0qWg0+0SChFe9oq0KAwEkVs6ZDMB2 P16MieEEQ6StQRlvy2YBv80L1TMl3T90Bo1UUn6ARXEpcbFE0/aORH/jEXcRteb+vuik5UGY 5TsyLYdPur3TXm7XDBdmmyQVJjnJKYK9AQxj95KlXLVO38lczsFNBFRjzmoBEACyAxbvUEhd GDGNg0JhDdezyTdN8C9BFsdxyTLnSH31NRiyp1QtuxvcqGZjb2trDVuCbIzRrgMZLVgo3upr MIOx1CXEgmn23Zhh0EpdVHM8IKx9Z7V0r+rrpRWFE8/wQZngKYVi49PGoZj50ZEifEJ5qn/H Nsp2+Y+bTUjDdgWMATg9DiFMyv8fvoqgNsNyrrZTnSgoLzdxr89FGHZCoSoAK8gfgFHuO54B lI8QOfPDG9WDPJ66HCodjTlBEr/Cwq6GruxS5i2Y33YVqxvFvDa1tUtl+iJ2SWKS9kCai2DR 3BwVONJEYSDQaven/EHMlY1q8Vln3lGPsS11vSUK3QcNJjmrgYxH5KsVsf6PNRj9mp8Z1kIG qjRx08+nnyStWC0gZH6NrYyS9rpqH3j+hA2WcI7De51L4Rv9pFwzp161mvtc6eC/GxaiUGuH BNAVP0PY0fqvIC68p3rLIAW3f97uv4ce2RSQ7LbsPsimOeCo/5vgS6YQsj83E+AipPr09Caj 0hloj+hFoqiticNpmsxdWKoOsV0PftcQvBCCYuhKbZV9s5hjt9qn8CE86A5g5KqDf83Fxqm/ vXKgHNFHE5zgXGZnrmaf6resQzbvJHO0Fb0CcIohzrpPaL3YepcLDoCCgElGMGQjdCcSQ+Ci FCRl0Bvyj1YZUql+ZkptgGjikQARAQABwsFfBBgBAgAJBQJUY85qAhsMAAoJEGg1lTBwyZKw l4IQAIKHs/9po4spZDFyfDjunimEhVHqlUt7ggR1Hsl/tkvTSze8pI1P6dGp2XW6AnH1iayn yRcoyT0ZJ+Zmm4xAH1zqKjWplzqdb/dO28qk0bPso8+1oPO8oDhLm1+tY+cOvufXkBTm+whm +AyNTjaCRt6aSMnA/QHVGSJ8grrTJCoACVNhnXg/R0g90g8iV8Q+IBZyDkG0tBThaDdw1B2l asInUTeb9EiVfL/Zjdg5VWiF9LL7iS+9hTeVdR09vThQ/DhVbCNxVk+DtyBHsjOKifrVsYep WpRGBIAu3bK8eXtyvrw1igWTNs2wazJ71+0z2jMzbclKAyRHKU9JdN6Hkkgr2nPb561yjcB8 sIq1pFXKyO+nKy6SZYxOvHxCcjk2fkw6UmPU6/j/nQlj2lfOAgNVKuDLothIxzi8pndB8Jju KktE5HJqUUMXePkAYIxEQ0mMc8Po7tuXdejgPMwgP7x65xtfEqI0RuzbUioFltsp1jUaRwQZ MTsCeQDdjpgHsj+P2ZDeEKCbma4m6Ez/YWs4+zDm1X8uZDkZcfQlD9NldbKDJEXLIjYWo1PH hYepSffIWPyvBMBTW2W5FRjJ4vLRrJSUoEfJuPQ3vW9Y73foyo/qFoURHO48AinGPZ7PC7TF vUaNOTjKedrqHkaOcqB185ahG2had0xnFsDPlx5y In-Reply-To: <20260618170913.GBajQmOQyOiBLqopUl@fat_crate.local> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/18/26 10:09, Borislav Petkov wrote: > On Wed, Jun 17, 2026 at 03:13:33PM -0700, Ihor Solodrai wrote: >> So my question to maintainers is what approach seems best? > The CPUID stuff is being rewritten currently and it should address your issue > too. If not, then we need to rewrite it better. > > Can you reproduce with this set applied ontop: > > https://lore.kernel.org/r/20260528153923.403473-1-darwi@linutronix.de Thinking about this a bit more... If Ahmed's series does fix this, I think it will be accidental. It still uses identify_cpu() and also does a memset() of the new c->cpuid structure in addition to the old c->x86_capability structure. I'm not knocking Ahmed's series by any means. It just probably won't fix this issue. In a perfect world early_identify_cpu() and identify_cpu() would either get consolidated into one thing. Or at least become two discrete things that initialize two completely disjoint sets of data. That way, identify_cpu() wouldn't memset() anything. Isn't that the _real_ fix? Instead of trying to hide the inconsistency when good data is blown away, we stop blowing it away in the first place?