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 6E0FAEE49A0 for ; Wed, 23 Aug 2023 09:52:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236102AbjHWJv6 (ORCPT ); Wed, 23 Aug 2023 05:51:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43920 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236151AbjHWJt3 (ORCPT ); Wed, 23 Aug 2023 05:49:29 -0400 Received: from smtp-fw-80009.amazon.com (smtp-fw-80009.amazon.com [99.78.197.220]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E9C497EC2; Wed, 23 Aug 2023 02:27:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.es; i=@amazon.es; q=dns/txt; s=amazon201209; t=1692782848; x=1724318848; h=message-id:date:mime-version:to:cc:references:from: in-reply-to:content-transfer-encoding:subject; bh=iK0hSqTp2Pv1usTBSU2LQaB5IvppSRAreY/km3cKtfo=; b=m8vqT7qNWf+hyqMwG0kQESNkci+rkHG86AaqBN+haFdk3HtL3yg+qikY Tez2f2JJ7fr9Vzk3QGlkzsfLBzU0ggq9psBh3Ftdd7+IIlJ2DN6Wzo4lG XYQJ5dge+OuKGS36R9IyOVqJ2hCkfGkEH2vnLbCRWUxD0ptxXRXjf1Jat Y=; X-IronPort-AV: E=Sophos;i="6.01,195,1684800000"; d="scan'208";a="24246244" Subject: Re: [RFC PATCH 1/2] random: emit reseed notifications for PRNGs Received: from pdx4-co-svc-p1-lb2-vlan2.amazon.com (HELO email-inbound-relay-iad-1e-m6i4x-9694bb9e.us-east-1.amazon.com) ([10.25.36.210]) by smtp-border-fw-80009.pdx80.corp.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Aug 2023 09:27:26 +0000 Received: from EX19D009EUA004.ant.amazon.com (iad12-ws-svc-p26-lb9-vlan2.iad.amazon.com [10.40.163.34]) by email-inbound-relay-iad-1e-m6i4x-9694bb9e.us-east-1.amazon.com (Postfix) with ESMTPS id 6CA3D8066C; Wed, 23 Aug 2023 09:27:22 +0000 (UTC) Received: from EX19D037EUB003.ant.amazon.com (10.252.61.119) by EX19D009EUA004.ant.amazon.com (10.252.50.97) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.30; Wed, 23 Aug 2023 09:27:21 +0000 Received: from [192.168.2.87] (10.1.212.9) by EX19D037EUB003.ant.amazon.com (10.252.61.119) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.37; Wed, 23 Aug 2023 09:27:16 +0000 Message-ID: Date: Wed, 23 Aug 2023 11:27:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Greg KH CC: Olivia Mackall , Herbert Xu , Theodore Ts'o , "Jason A. Donenfeld" , "Michael S. Tsirkin" , "Jason Wang" , Xuan Zhuo , , , , , , , References: <20230823090107.65749-1-bchalios@amazon.es> <20230823090107.65749-2-bchalios@amazon.es> <2023082322-semester-heave-e5bc@gregkh> Content-Language: en-US From: Babis Chalios Autocrypt: addr=bchalios@amazon.es; keydata= xsFNBGIonY4BEACl1/Qf/fYoDawcFfvjckR5H2yDxlBvKoFT4m5KYiRUivcf5nwCijrM3Fij d38MBpMb9kvwN7lAXOXPCBZMhaNH3J3NuFpUCIZ+UZtf5JgDGiKd/Obli/c0m+7du8wEysCD Z1ldpDeW3c9aENw/uUChQkTEEh0Cmj83uVYEz+BMJKmeA/1Qz0kzGp/MkW8mZYVY5ts4PcBq UmH8Qm5x9NqspTMqIj/yUyxFgxRcKzBOPCF7KiabuCNGCWJAL3EN4SQIQ4MsLBJOSyk5RazC 5x4Vdt9+oCq+jD6H5S19FBSiXKDZCFitIQYd9Xj3Stw6jgrObWrn4ll3aT/XCMYF0Ja8x9+S /UfYEGEPOJkrelKqAu1721LcBwG1rPp12uzyTmtwWBIeDp15/ZnxZ5IG1HuNSsoZzjjnhiLY ECfIymLMya2ofSk4ENCbAdmCAmuI5Fe5ZcUR5zjKHIN5aTgPYEf0H17iZMZlhJ7tAFFKnaGR gMzPiJaff1B8fJjaRd6S73f+4hK0elXAAphoeg8nM2EQQAEzIqSocAZgiktsTbfDSuvCFjrc NP3/R5gWdJDbhlMGP+bhs6HclywzkahskxEQtHo4C1tjP5XFxmUhYlJWJHncDJa4jlouo3zo 1h1NE3OPbT1HDj8O69GXcNZop10hMbnlrIYb3HfJEpTIudYPGwARAQABzSJCYWJpcyBDaGFs aW9zIDxiY2hhbGlvc0BhbWF6b24uZXM+wsGSBBMBCAA8FiEEDnV+NQfr1LBsLB/GjBB7GAqe ZsQFAmIonY4CGwMFCwkIBwIDIgIBBhUKCQgLAgQWAgMBAh4HAheAAAoJEIwQexgKnmbEK2AP /3E4c+xwberE/Sczr5YtO2NZDOnJ0ksumNBJYwJxVNvZEKG1tzJ03oxAE7v0xNylCXSV+tEk WUxuwcyeisQwfwlhhG3upW0ErvpLqhhWXZQYV2ogI3ZJ54oBuFqCkHQ5MOlIApUI5jR6rzY4 0i8c+1DWL3VI4Jmj8+QRfLxPbade81Rj7j/jc7qTsyzfs4SVRQQo2AF6VBIqNh9MFwJzeX4a 8INhNwchKpt8xUfRSSR5Q/FhrS4drUaG4Hi+dL1aPLWpo9zvFCJQpOeDQysrIyQ7m8VZO0cn Iqh6vnfJrcx4vxQB19XJHM6sufmHLfEy/gZAXplq1YPpuzy6m0Kj5oUABRsAQDPulSndV2qL d8cgAgVei/SEhl6qDmNQqtTK3GeqgdyUHvIYD+MyzTsDplSiA2wvLVdbeltPdi+KmA7kyE7B qthH1H7AMr8IOqBNUS6oVNGD72Bg5qEenhiUgMI287UyGPz3TxAPdwc3TFCxHaJeNhLpi1Db F2tdIxBlwtbwHI9ah24lpmDyO+nttbXv6wJWgg4oV2Dw7lgYh2t9YBnQvI3xO+c2AbDwBEOe 9daTNJYVnjboCPjF/HiJAJh2aurno5Da72gyRsEf3cl/R5rIIx2ZfZVwk88MTZSe4dwsu2NV l6yT6DyyLWdZcSjmkLuuW92THzlkZlpQ0EDqzsFNBGIonY4BEADCxlifRJR46flvWYp6xRjp pppGljP69wCJQSGdOSQj2KwIZbqwI36NCW8zCXAYUrpMqNhsp2pc1IUnv7P9HBitx4t8XCMV Cj+ZRXOZs3fGvYxOH433+UuDt4bC7Nazq6fFJkdUgZoivXOqzJpLmjSTtxJBnbv/CFmo7tgM PG+gHZUzlwATc4iYqc23OKHyaVA1OecU4CJoVKLP0vwO/xaSEs7jL0MYHqSYTBN/63A9Xqt3 JBLUuwGs1a936xXq1/MMLWRAP1N5XGL0S7oOF9TM2trq2GISaBVenjpWhT11X+q67y3cFxbb oETa14ggq9QKorgXVgYWUa7Jq5hBlRiJQeR+gAa8jUTIU0c7psgz24CEwC1TDx9TpDz1BMIn /zEF8g7j8nZlqiph5qyqbSc9iayhtf2FG0aYNBEzgybKoR50qEIM82pHCeJSYZxpPILdCVWn tntD+h22IJFHgXihCYPYkHa//Nyb2+Alh2hBsRulQWNRyubG+HZvW/Mre7kyVbJi+ajEkx6K /pbxWbJlDp2ozgnDRTf+7/xCKVP9jO2Y6JjrRx8WAlqYSjK16ML9w1hxZepekeOXhNxGxhEH Z5lzVEVdbHQUN69ZFOcjZnf87vMZBcPxzebcydzRs96CFYsEkT34C9SnElejzuNmN5fMfrJ9 713Mj0/MdpcjPwARAQABwsF2BBgBCAAgFiEEDnV+NQfr1LBsLB/GjBB7GAqeZsQFAmIonY4C GwwACgkQjBB7GAqeZsR2Lg/8CIRvePonn3me+500Zdyv3Z3yaIkHv9mArCLPOzh0mhwrWQWh e5oLnTx51ynU5kUow0i3Owj6xu972naqpV/c0olGdNrwrYboKM3DMHrdZr/pqGhWckU+8S2T uCVB3c/b8YRxqXww5GhwV1WwFC4sndc86tl1yKpxpDdQ858uZYs33Ur+WmxJJQ5BD6sQ48OD 5hEseFrcbikSKk/eVD1FrT3lzbaVqqvQ71soCYYuo2VKxmShuQxUeeFp8hnDw3TR5SO1KJft CT6sQ4dS3vUDeKzVu8E2ofGyOQZ9j6KlFz9daBiRHowFON1vZKS/k8A7ZCZ5Co3Skx538GW8 jDNZJgnSbaam8FVDT1z2H6irmEHz1/vb3hZns0bAmqgwWONTW/gO5jcPbzbTqPfIlmCEtBDf qGaQH7uIyC5kPMTQCNvEMKKn/R2hV3al2/gLvRYFI1GGFE/QdLXiYXmtkDBaz/niHxUUGqO4 LbSF+KYpZYewC8Wx5gTr4Glj+9+RcDWzdkGBd+Kthh0VIOdalbjbnv2jmt5gvLoeLDNpIZRQ AQ+HulTHw5frK1j8+AHIKQYXIE8xXzVkssNuX0Hc7ecC5jm/XlGr5IuQkJpFyVtiXfjkd6tq 9CfKbXmQEUz/yWPkXerBltQSv7ePqJHPFMwJrFAqFftGK6t9nvzGjQB91RM= In-Reply-To: <2023082322-semester-heave-e5bc@gregkh> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.1.212.9] X-ClientProxiedBy: EX19D032UWA002.ant.amazon.com (10.13.139.81) To EX19D037EUB003.ant.amazon.com (10.252.61.119) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Greg, On 23/8/23 11:08, Greg KH wrote: > CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe. > > > > On Wed, Aug 23, 2023 at 11:01:05AM +0200, Babis Chalios wrote: >> Sometimes, PRNGs need to reseed. For example, on a regular timer >> interval, to ensure nothing consumes a random value for longer than e.g. >> 5 minutes, or when VMs get cloned, to ensure seeds don't leak in to >> clones. >> >> The notification happens through a 32bit epoch value that changes every >> time cached entropy is no longer valid, hence PRNGs need to reseed. User >> space applications can get hold of a pointer to this value through >> /dev/(u)random. We introduce a new ioctl() that returns an anonymous >> file descriptor. From this file descriptor we can mmap() a single page >> which includes the epoch at offset 0. >> >> random.c maintains the epoch value in a global shared page. It exposes >> a registration API for kernel subsystems that are able to notify when >> reseeding is needed. Notifiers register with random.c and receive a >> unique 8bit ID and a pointer to the epoch. When they need to report a >> reseeding event they write a new epoch value which includes the >> notifier ID in the first 8 bits and an increasing counter value in the >> remaining 24 bits: >> >> RNG epoch >> *-------------*---------------------* >> | notifier id | epoch counter value | >> *-------------*---------------------* >> 8 bits 24 bits > Why not just use 32/32 for a full 64bit value, or better yet, 2 > different variables? Why is 32bits and packing things together here > somehow simpler? We made it 32 bits so that we can read/write it atomically in all 32bit architectures. Do you think that's not a problem? Cheers, Babis