From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Theodore Ts'o" Subject: Re: [PATCH v4 05/16] fs-verity: add Kconfig and the helper functions for hashing Date: Sat, 15 Jun 2019 08:57:31 -0400 Message-ID: <20190615125731.GF6142@mit.edu> References: <20190606155205.2872-1-ebiggers@kernel.org> <20190606155205.2872-6-ebiggers@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-2.v29.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1hc8Fe-0002UH-ET for linux-f2fs-devel@lists.sourceforge.net; Sat, 15 Jun 2019 12:57:46 +0000 Received: from outgoing-auth-1.mit.edu ([18.9.28.11] helo=outgoing.mit.edu) by sfi-mx-4.v28.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) id 1hc8Fd-00EwpE-67 for linux-f2fs-devel@lists.sourceforge.net; Sat, 15 Jun 2019 12:57:46 +0000 Content-Disposition: inline In-Reply-To: <20190606155205.2872-6-ebiggers@kernel.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net To: Eric Biggers Cc: "Darrick J . Wong" , linux-api@vger.kernel.org, Dave Chinner , linux-f2fs-devel@lists.sourceforge.net, linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org, Jaegeuk Kim , linux-integrity@vger.kernel.org, linux-ext4@vger.kernel.org, Linus Torvalds , Christoph Hellwig , Victor Hsieh On Thu, Jun 06, 2019 at 08:51:54AM -0700, Eric Biggers wrote: > From: Eric Biggers > > Add the beginnings of the fs/verity/ support layer, including the > Kconfig option and various helper functions for hashing. To start, only > SHA-256 is supported, but other hash algorithms can easily be added. > > Signed-off-by: Eric Biggers Looks good; you can add: Reviewed-off-by: Theodore Ts'o One thought for consideration below... > + > +/* > + * Maximum depth of the Merkle tree. Up to 64 levels are theoretically possible > + * with a very small block size, but we'd like to limit stack usage during > + * verification, and in practice this is plenty. E.g., with SHA-256 and 4K > + * blocks, a file with size UINT64_MAX bytes needs just 8 levels. > + */ > +#define FS_VERITY_MAX_LEVELS 16 Maybe we should make FS_VERITY_MAX_LEVELS 8 for now? This is an implementation-level restriction, and currently we don't support any architectures that have a page size < 4k. We can always bump this number up in the future if it ever becomes necessary, and limiting max levels to 8 saves almost 100 bytes of stack space in verify_page(). - Ted 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 X-Spam-Level: X-Spam-Status: No, score=-5.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E1343C31E50 for ; Sat, 15 Jun 2019 12:57:48 +0000 (UTC) Received: from lists.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A49D121773; Sat, 15 Jun 2019 12:57:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=sourceforge.net header.i=@sourceforge.net header.b="G46fWvr9"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=sf.net header.i=@sf.net header.b="LU43LQCG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A49D121773 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=mit.edu Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-f2fs-devel-bounces@lists.sourceforge.net Received: from [127.0.0.1] (helo=sfs-ml-2.v29.lw.sourceforge.com) by sfs-ml-2.v29.lw.sourceforge.com with esmtp (Exim 4.90_1) (envelope-from ) id 1hc8Ff-0002UQ-Rp; Sat, 15 Jun 2019 12:57:47 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-2.v29.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1hc8Fe-0002UH-ET for linux-f2fs-devel@lists.sourceforge.net; Sat, 15 Jun 2019 12:57:46 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=In-Reply-To:Content-Type:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=6QcU/umXcetbwZjIIBHnh75TA30pZfdg6hUgtoFwrcA=; b=G46fWvr9Gx4cO661SRF2B9R5h4 IQnoJAScVIh9A2k5Ev/PpxtHlfCJUjEWCKD1EqiwIDEPjOLCVOWm30X84NRva5YeTj/6fT1PWCV1f oFH/x2kE0Ta6a6ZKUeh0DmvTzvtARlaChAGT0VJzFy3HSoc8983JmlWgtN2o+NN7RUnQ=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To :From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=6QcU/umXcetbwZjIIBHnh75TA30pZfdg6hUgtoFwrcA=; b=LU43LQCG4w9ioeRRi+6PbTjPfn xqmSUg7aR8lIz8UNGFvoYOCNQ5wdGg7aOWqYQSaOqlobYEf5nPlN+iSwCZOI+O2F/PRtXnUZFObaE kIcVAPbrp1tMwBTLEOIHNXoatyn2HnQRTZ1Sz7iL6T2vahZSS+/gg+A6RPRWRh9ZkzkI=; Received: from outgoing-auth-1.mit.edu ([18.9.28.11] helo=outgoing.mit.edu) by sfi-mx-4.v28.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) id 1hc8Fd-00EwpE-67 for linux-f2fs-devel@lists.sourceforge.net; Sat, 15 Jun 2019 12:57:46 +0000 Received: from callcc.thunk.org (rrcs-74-87-88-165.west.biz.rr.com [74.87.88.165]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id x5FCvWOZ003473 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sat, 15 Jun 2019 08:57:33 -0400 Received: by callcc.thunk.org (Postfix, from userid 15806) id 0D4F8420484; Sat, 15 Jun 2019 08:57:32 -0400 (EDT) Date: Sat, 15 Jun 2019 08:57:31 -0400 From: "Theodore Ts'o" To: Eric Biggers Message-ID: <20190615125731.GF6142@mit.edu> References: <20190606155205.2872-1-ebiggers@kernel.org> <20190606155205.2872-6-ebiggers@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190606155205.2872-6-ebiggers@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Headers-End: 1hc8Fd-00EwpE-67 Subject: Re: [f2fs-dev] [PATCH v4 05/16] fs-verity: add Kconfig and the helper functions for hashing X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Darrick J . Wong" , linux-api@vger.kernel.org, Dave Chinner , linux-f2fs-devel@lists.sourceforge.net, linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org, Jaegeuk Kim , linux-integrity@vger.kernel.org, linux-ext4@vger.kernel.org, Linus Torvalds , Christoph Hellwig , Victor Hsieh Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net Message-ID: <20190615125731.4WmHekoOyTuUna88tPq2O0YvxieZSm1SvR6jvreC3v8@z> On Thu, Jun 06, 2019 at 08:51:54AM -0700, Eric Biggers wrote: > From: Eric Biggers > > Add the beginnings of the fs/verity/ support layer, including the > Kconfig option and various helper functions for hashing. To start, only > SHA-256 is supported, but other hash algorithms can easily be added. > > Signed-off-by: Eric Biggers Looks good; you can add: Reviewed-off-by: Theodore Ts'o One thought for consideration below... > + > +/* > + * Maximum depth of the Merkle tree. Up to 64 levels are theoretically possible > + * with a very small block size, but we'd like to limit stack usage during > + * verification, and in practice this is plenty. E.g., with SHA-256 and 4K > + * blocks, a file with size UINT64_MAX bytes needs just 8 levels. > + */ > +#define FS_VERITY_MAX_LEVELS 16 Maybe we should make FS_VERITY_MAX_LEVELS 8 for now? This is an implementation-level restriction, and currently we don't support any architectures that have a page size < 4k. We can always bump this number up in the future if it ever becomes necessary, and limiting max levels to 8 saves almost 100 bytes of stack space in verify_page(). - Ted _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel