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=-16.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 8BEC1C433DB for ; Thu, 28 Jan 2021 01:13:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 44A9864DDB for ; Thu, 28 Jan 2021 01:13:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231151AbhA1BNP (ORCPT ); Wed, 27 Jan 2021 20:13:15 -0500 Received: from mail.kernel.org ([198.145.29.99]:36374 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231699AbhA1BLX (ORCPT ); Wed, 27 Jan 2021 20:11:23 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9DC8960C40; Thu, 28 Jan 2021 01:10:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1611796242; bh=v3T7ujwKzSnkDtCCImiUZpKv0YgdS5KXdKZ00euqCw4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RV991imw0fVh9WuRc7VZ1451DK+8xNudMlmBSu97HfL/HcAG9EyJ1e7YNloQE4ILz elCgFA61wcaut5wzKbnnk0ifs0RqDiLl723PFM9yyMWgnrRpNhKQxPfoG+XgvL1kUy 6XlI59+no6iuAZSuD5reFegb6Qb9+WUT9LWC57KFskhN80VGRPn/QMZer4GyYh9gNk d7yXXDc+QS4mYUHJnrhMH0ElxbMnh4dqMZ7u/itMFe7DChNCgDNEo0tngRwOrRk/0i uj0s1HyPFsKM1vELAsrjK1+RWRRBPjBj4kV82JwQ4ZQbhmIZ/FASrnPH+4oWOAT5AF E/nbh2iHNYlMg== Date: Wed, 27 Jan 2021 17:10:39 -0800 From: Jaegeuk Kim To: Eric Biggers Cc: linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-api@vger.kernel.org, Theodore Ts'o , Victor Hsieh Subject: Re: [PATCH 4/6] fs-verity: support reading Merkle tree with ioctl Message-ID: References: <20210115181819.34732-1-ebiggers@kernel.org> <20210115181819.34732-5-ebiggers@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210115181819.34732-5-ebiggers@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 01/15, Eric Biggers wrote: > From: Eric Biggers > > Add support for FS_VERITY_METADATA_TYPE_MERKLE_TREE to > FS_IOC_READ_VERITY_METADATA. This allows a userspace server program to > retrieve the Merkle tree of a verity file for serving to a client which > implements fs-verity compatible verification. See the patch which > introduced FS_IOC_READ_VERITY_METADATA for more details. > > This has been tested using a new xfstest which calls this ioctl via a > new subcommand for the 'fsverity' program from fsverity-utils. > > Signed-off-by: Eric Biggers > --- > Documentation/filesystems/fsverity.rst | 10 +++- > fs/verity/read_metadata.c | 70 ++++++++++++++++++++++++++ > include/uapi/linux/fsverity.h | 2 + > 3 files changed, 81 insertions(+), 1 deletion(-) > > diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst > index 9ef7a7de60085..50b47a6d9ea11 100644 > --- a/Documentation/filesystems/fsverity.rst > +++ b/Documentation/filesystems/fsverity.rst > @@ -234,6 +234,8 @@ need this ioctl. > > This ioctl takes in a pointer to the following structure:: > > + #define FS_VERITY_METADATA_TYPE_MERKLE_TREE 1 > + > struct fsverity_read_metadata_arg { > __u64 metadata_type; > __u64 offset; > @@ -242,7 +244,13 @@ This ioctl takes in a pointer to the following structure:: > __u64 __reserved; > }; > > -``metadata_type`` specifies the type of metadata to read. > +``metadata_type`` specifies the type of metadata to read: > + > +- ``FS_VERITY_METADATA_TYPE_MERKLE_TREE`` reads the blocks of the > + Merkle tree. The blocks are returned in order from the root level > + to the leaf level. Within each level, the blocks are returned in > + the same order that their hashes are themselves hashed. > + See `Merkle tree`_ for more information. > > The semantics are similar to those of ``pread()``. ``offset`` > specifies the offset in bytes into the metadata item to read from, and > diff --git a/fs/verity/read_metadata.c b/fs/verity/read_metadata.c > index 43be990fd53e4..0f8ad2991cf90 100644 > --- a/fs/verity/read_metadata.c > +++ b/fs/verity/read_metadata.c > @@ -7,8 +7,75 @@ > > #include "fsverity_private.h" > > +#include > +#include > +#include > #include > > +static int fsverity_read_merkle_tree(struct inode *inode, > + const struct fsverity_info *vi, > + void __user *buf, u64 offset, int length) > +{ > + const struct fsverity_operations *vops = inode->i_sb->s_vop; > + u64 end_offset; > + unsigned int offs_in_page; > + pgoff_t index, last_index; > + int retval = 0; > + int err = 0; > + > + end_offset = min(offset + length, vi->tree_params.tree_size); > + if (offset >= end_offset) > + return 0; > + offs_in_page = offset_in_page(offset); > + last_index = (end_offset - 1) >> PAGE_SHIFT; > + > + /* > + * Iterate through each Merkle tree page in the requested range and copy > + * the requested portion to userspace. Note that the Merkle tree block > + * size isn't important here, as we are returning a byte stream; i.e., > + * we can just work with pages even if the tree block size != PAGE_SIZE. > + */ > + for (index = offset >> PAGE_SHIFT; index <= last_index; index++) { > + unsigned long num_ra_pages = > + min_t(unsigned long, last_index - index + 1, > + inode->i_sb->s_bdi->io_pages); > + unsigned int bytes_to_copy = min_t(u64, end_offset - offset, > + PAGE_SIZE - offs_in_page); > + struct page *page; > + const void *virt; > + > + page = vops->read_merkle_tree_page(inode, index, num_ra_pages); > + if (IS_ERR(page)) { > + err = PTR_ERR(page); > + fsverity_err(inode, > + "Error %d reading Merkle tree page %lu", > + err, index); > + break; > + } > + > + virt = kmap(page); > + if (copy_to_user(buf, virt + offs_in_page, bytes_to_copy)) { > + kunmap(page); > + put_page(page); > + err = -EFAULT; > + break; > + } > + kunmap(page); > + put_page(page); > + > + retval += bytes_to_copy; > + buf += bytes_to_copy; > + offset += bytes_to_copy; > + > + if (fatal_signal_pending(current)) { > + err = -EINTR; > + break; > + } > + cond_resched(); > + offs_in_page = 0; > + } Minor thought: How about invalidating or truncating merkel tree pages? Reviewed-by: Jaegeuk Kim > + return retval ? retval : err; > +} > /** > * fsverity_ioctl_read_metadata() - read verity metadata from a file > * @filp: file to read the metadata from > @@ -48,6 +115,9 @@ int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg) > buf = u64_to_user_ptr(arg.buf_ptr); > > switch (arg.metadata_type) { > + case FS_VERITY_METADATA_TYPE_MERKLE_TREE: > + return fsverity_read_merkle_tree(inode, vi, buf, arg.offset, > + length); > default: > return -EINVAL; > } > diff --git a/include/uapi/linux/fsverity.h b/include/uapi/linux/fsverity.h > index e062751294d01..94003b153cb3d 100644 > --- a/include/uapi/linux/fsverity.h > +++ b/include/uapi/linux/fsverity.h > @@ -83,6 +83,8 @@ struct fsverity_formatted_digest { > __u8 digest[]; > }; > > +#define FS_VERITY_METADATA_TYPE_MERKLE_TREE 1 > + > struct fsverity_read_metadata_arg { > __u64 metadata_type; > __u64 offset; > -- > 2.30.0