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Fri, 19 Jun 2020 06:38:11 +0000 Received: from DGGEMS412-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id DBE6EBE6350EF092C04C; Fri, 19 Jun 2020 14:37:54 +0800 (CST) Received: from [10.134.22.195] (10.134.22.195) by smtp.huawei.com (10.3.19.212) with Microsoft SMTP Server (TLS) id 14.3.487.0; Fri, 19 Jun 2020 14:37:52 +0800 To: Eric Biggers References: <20200617075732.213198-1-satyat@google.com> <20200617075732.213198-4-satyat@google.com> <5e78e1be-f948-d54c-d28e-50f1f0a92ab3@huawei.com> <20200618181357.GC2957@sol.localdomain> <20200619042048.GF2957@sol.localdomain> From: Chao Yu Message-ID: Date: Fri, 19 Jun 2020 14:37:52 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20200619042048.GF2957@sol.localdomain> Content-Language: en-US X-Originating-IP: [10.134.22.195] X-CFilter-Loop: Reflected X-Headers-End: 1jmAfB-00Be2Y-99 Subject: Re: [f2fs-dev] [PATCH 3/4] f2fs: add inline encryption support 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: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-fscrypt@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, Satya Tangirala Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On 2020/6/19 12:20, Eric Biggers wrote: > On Fri, Jun 19, 2020 at 10:39:34AM +0800, Chao Yu wrote: >> Hi Eric, >> >> On 2020/6/19 2:13, Eric Biggers wrote: >>> Hi Chao, >>> >>> On Thu, Jun 18, 2020 at 06:06:02PM +0800, Chao Yu wrote: >>>>> @@ -936,8 +972,11 @@ void f2fs_submit_page_write(struct f2fs_io_info *fio) >>>>> >>>>> inc_page_count(sbi, WB_DATA_TYPE(bio_page)); >>>>> >>>>> - if (io->bio && !io_is_mergeable(sbi, io->bio, io, fio, >>>>> - io->last_block_in_bio, fio->new_blkaddr)) >>>>> + if (io->bio && >>>>> + (!io_is_mergeable(sbi, io->bio, io, fio, io->last_block_in_bio, >>>>> + fio->new_blkaddr) || >>>>> + !f2fs_crypt_mergeable_bio(io->bio, fio->page->mapping->host, >>>>> + fio->page->index, fio))) >>>> >>>> bio_page->index, fio))) >>>> >>>>> __submit_merged_bio(io); >>>>> alloc_new: >>>>> if (io->bio == NULL) { >>>>> @@ -949,6 +988,8 @@ void f2fs_submit_page_write(struct f2fs_io_info *fio) >>>>> goto skip; >>>>> } >>>>> io->bio = __bio_alloc(fio, BIO_MAX_PAGES); >>>>> + f2fs_set_bio_crypt_ctx(io->bio, fio->page->mapping->host, >>>>> + fio->page->index, fio, GFP_NOIO); >>>> >>>> bio_page->index, fio, GFP_NOIO); >>>> >>> >>> We're using ->mapping->host and ->index. Ordinarily that would mean the page >>> needs to be a pagecache page. But bio_page can also be a compressed page or a >>> bounce page containing fs-layer encrypted contents. >> >> I'm concerning about compression + inlinecrypt case. >> >>> >>> Is your suggestion to keep using fio->page->mapping->host (since encrypted pages >> >> Yup, >> >>> don't have a mapping), but start using bio_page->index (since f2fs apparently >> >> I meant that we need to use bio_page->index as tweak value in write path to >> keep consistent as we did in read path, otherwise we may read the wrong >> decrypted data later to incorrect tweak value. >> >> - f2fs_read_multi_pages (only comes from compression inode) >> - f2fs_alloc_dic >> - f2fs_set_compressed_page(page, cc->inode, >> start_idx + i + 1, dic); >> ^^^^^^^^^^^^^^^^^ >> - dic->cpages[i] = page; >> - for () >> struct page *page = dic->cpages[i]; >> if (!bio) >> - f2fs_grab_read_bio(..., page->index,..) >> - f2fs_set_bio_crypt_ctx(..., first_idx, ..) /* first_idx == cpage->index */ >> >> You can see that cpage->index was set to page->index + 1, that's why we need >> to use one of cpage->index/page->index as tweak value all the time rather than >> using both index mixed in read/write path. >> >> But note that for fs-layer encryption, we have used cpage->index as tweak value, >> so here I suggest we can keep consistent to use cpage->index in inlinecrypt case. > > Yes, inlinecrypt mustn't change the ciphertext that gets written to disk. > >> >>> *does* set ->index for compressed pages, and if the file uses fs-layer >>> encryption then f2fs_set_bio_crypt_ctx() won't use the index anyway)? >>> >>> Does this mean the code is currently broken for compression + inline encryption >>> because it's using the wrong ->index? I think the answer is no, since >> >> I guess it's broken now for compression + inlinecrypt case. >> >>> f2fs_write_compressed_pages() will still pass the first 'nr_cpages' pagecache >>> pages along with the compressed pages. In that case, your suggestion would be a >>> cleanup rather than a fix? >> >> That's a fix. >> > > FWIW, I tested this, and it actually works both before and after your suggested > change. The reason is that f2fs_write_compressed_pages() actually passes the > pagecache pages sequentially starting at 'start_idx_of_cluster(cc) + 1' for the > length of the compressed cluster. That matches the '+ 1' adjustment elsewhere, > so we have fio->page->index == bio_page->index. I've checked the code, yes, that's correct. > > I personally think the way the f2fs compression code works is really confusing. > Compressed pages don't have a 1:1 correspondence to pagecache pages, so there > should *not* be a pagecache page passed around when writing a compressed page. The only place we always use fio->page is: - f2fs_submit_page_write - trace_f2fs_submit_page_write(fio->page,..) - f2fs__submit_page_bio __entry->dev = page_file_mapping(page)->host->i_sb->s_dev; __entry->ino = page_file_mapping(page)->host->i_ino; For compression case, we can get rid of using this parameter because bio_page (fio->compressed_page) has correct mapping info, however for fs-layer encryption case, bio_page (fio->encrypted_page, allocated by fscrypt_alloc_bounce_page()) has not correct mapping info. > > Anyway, here's the test script I used in case anyone else wants to use it. But > we really need to write a proper f2fs compression + encryption test for xfstests > which decrypts and decompresses a file in userspace and verifies we get back the > original data. (There are already ciphertext verification tests, but they don't > cover compression.) Note that this test is needed even for the filesystem-layer > encryption which is currently supported. Yes, let me check how to make this testcase a bit later. > > #!/bin/bash > > set -e > > DEV=/dev/vdb > > umount /mnt &> /dev/null || true > mkfs.f2fs -f -O encrypt,compression,extra_attr $DEV > head -c 1000000 /dev/zero > /tmp/testdata > > for opt1 in '-o inlinecrypt' ''; do > mount $DEV /mnt $opt1 > rm -rf /mnt/.fscrypt /mnt/dir > fscrypt setup /mnt > mkdir /mnt/dir > chattr +c /mnt/dir > echo hunter2 | fscrypt encrypt /mnt/dir --quiet --source=custom_passphrase --name=secret > cp /tmp/testdata /mnt/dir/file > umount /mnt > for opt2 in '-o inlinecrypt' ''; do > mount $DEV /mnt $opt2 > echo hunter2 | fscrypt unlock /mnt/dir --quiet > cmp /mnt/dir/file /tmp/testdata > umount /mnt > done > done > . > _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel