linux-kernel - Re: [PATCH v8 0/8] Support for Casefolding and Encryption

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Date:   Fri, 6 Mar 2020 21:08:00 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Daniel Rosenberg <drosen@...gle.com>
Cc:     Theodore Ts'o <tytso@....edu>, linux-ext4@...r.kernel.org,
        Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-fscrypt@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Richard Weinberger <richard@....at>,
        linux-mtd@...ts.infradead.org,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel-team@...roid.com
Subject: Re: [PATCH v8 0/8] Support for Casefolding and Encryption

On Fri, Mar 06, 2020 at 06:36:03PM -0800, Daniel Rosenberg wrote:
> These patches are all on top of torvalds/master
> 
> Ext4 and F2FS currently both support casefolding and encryption, but not at
> the same time. These patches aim to rectify that.
> 
> I've left off the Ext4 patches that enable casefolding and ecryption from
> this revision since they still need some fixups, and I haven't gotten around
> to the fsck changes yet.
> 
> I moved the identical casefolding dcache operations for ext4 and f2fs into
> fs/libfs.c, as all filesystems using casefolded names will want them.
> 
> I've also adjust fscrypt to not set it's d_revalidate operation during it's
> prepare lookup, instead having the calling filesystem set it up. This is
> done to that the filesystem may have it's own dentry_operations. Also added
> a helper function in libfs.c that will work for filesystems supporting both
> casefolding and fscrypt.
> 
> For Ext4, since the hash for encrypted casefolded directory names cannot be
> computed without the key, we need to store the hash on disk. We only do so
> for encrypted and casefolded directories to avoid on disk format changes.
> Previously encryption and casefolding could not be on the same filesystem,
> and we're relaxing that requirement. F2fs is a bit more straightforward
> since it already stores hashes on disk.
> 
> I've updated the related tools with just enough to enable the feature. I
> still need to adjust ext4's fsck's, although without access to the keys,
> neither fsck will be able to verify the hashes of casefolded and encrypted
> names.
> 

Can you please do some more testing?  Just playing around with casefolding (not
even encryption yet), it didn't take long to notice some problems.  E.g.

$ mkfs.f2fs -f -C utf8 /dev/vdc
$ mount /vdc
$ mkdir /vdc/dir
$ chattr +F /vdc/dir
$ echo foo > /vdc/dir/a
$ cat /vdc/dir/A
foo
$ rm /vdc/dir/a
$ cat /vdc/dir/A
foo

I.e. 'rm' only deleted "a", not "A", even though they're the same file.

Also, there's a casefolding test in xfstests, and with this patchset applied it
fails and causes kernel warnings.  It passes without this patchset applied.

$ kvm-xfstests -c f2fs -g casefold

[...]
[    5.947961] ------------[ cut here ]------------
[    5.948714] WARNING: CPU: 1 PID: 1053 at fs/inode.c:302 drop_nlink+0x1e/0x30
[    5.949742] CPU: 1 PID: 1053 Comm: rm Not tainted 5.6.0-rc4-00008-gf9c20981ece1 #4
[    5.950835] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20191223_100556-anatol 04/01/2014
[    5.952234] RIP: 0010:drop_nlink+0x1e/0x30
[    5.952838] Code: 44 24 10 eb da 0f 0b 0f 1f 44 00 00 8b 47 40 8d 50 ff 85 c0 74 14 85 d2 89 57 40 75 0c 48 8b 47 28 f0 48 ff 80 98 5
[    5.955509] RSP: 0018:ffffc90001633d60 EFLAGS: 00010246
[    5.956273] RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000000000
[    5.957303] RDX: 00000000ffffffff RSI: 0000000000000001 RDI: ffff88807a84d688
[    5.958332] RBP: ffffc90001633d90 R08: 0000000000000000 R09: 0000000000000000
[    5.959363] R10: 0000000000000000 R11: 0000000000000000 R12: ffff88807a84d688
[    5.960392] R13: ffff88807cf97648 R14: ffff88807a84da50 R15: ffff8880776bc000
[    5.961424] FS:  00007f7003d12540(0000) GS:ffff88807fd00000(0000) knlGS:0000000000000000
[    5.962588] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    5.963422] CR2: 000055a037bf5448 CR3: 00000000780ad000 CR4: 00000000003406e0
[    5.964453] Call Trace:
[    5.964828]  ? f2fs_drop_nlink+0x56/0x140
[    5.965417]  f2fs_delete_inline_entry+0x19e/0x1e0
[    5.966106]  f2fs_delete_entry+0x1be/0x320
[    5.966705]  f2fs_unlink+0x10c/0x360
[    5.967239]  vfs_unlink+0xf1/0x1d0
[    5.967747]  do_unlinkat+0x188/0x2c0
[    5.968254]  __x64_sys_unlinkat+0x33/0x50
[    5.968709]  do_syscall_64+0x4a/0x1f0
[    5.969130]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[    5.969533] RIP: 0033:0x7f7003c3bff7
[    5.969804] Code: 73 01 c3 48 8b 0d 99 ee 0c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 07 01 8
[    5.971154] RSP: 002b:00007ffde2c23588 EFLAGS: 00000206 ORIG_RAX: 0000000000000107
[    5.971707] RAX: ffffffffffffffda RBX: 000055a037bf5570 RCX: 00007f7003c3bff7
[    5.972242] RDX: 0000000000000000 RSI: 000055a037bf4340 RDI: 00000000ffffff9c
[    5.972774] RBP: 000055a037bf42b0 R08: 0000000000000003 R09: 0000000000000000
[    5.973305] R10: fffffffffffffbd8 R11: 0000000000000206 R12: 00007ffde2c23770
[    5.973837] R13: 0000000000000000 R14: 000055a037bf5570 R15: 0000000000000000
[    5.974367] irq event stamp: 1134
[    5.974621] hardirqs last  enabled at (1133): [<ffffffff810f6645>] ktime_get_coarse_real_ts64+0x95/0xb0
[    5.975321] hardirqs last disabled at (1134): [<ffffffff81001b79>] trace_hardirqs_off_thunk+0x1a/0x1c
[    5.976003] softirqs last  enabled at (502): [<ffffffff8102ab53>] fpu__clear+0xb3/0x1b0
[    5.976586] softirqs last disabled at (500): [<ffffffff8102ab15>] fpu__clear+0x75/0x1b0
[    5.977181] ---[ end trace 31b6c5defdf04f01 ]---
[    5.989770] ------------[ cut here ]------------
[...]
[failed, exit status 1] [21:03:50]- output mismatch (see /results/f2fs/results-default/generic/556.out.bad)
    --- tests/generic/556.out	2020-02-18 11:22:36.000000000 -0800
    +++ /results/f2fs/results-default/generic/556.out.bad	2020-03-06 21:03:50.783730049 -0800
    @@ -12,5 +12,5 @@
     # file: SCRATCH_MNT/xattrs/x/f1
     user.foo="bar"
     
    -touch: setting times of 'SCRATCH_MNT/strict/corac'$'\314\247\303': Invalid argument
    -touch: setting times of 'SCRATCH_MNT/strict/cora'$'\303\247\303': Invalid argument
    +_check_generic_filesystem: filesystem on /dev/vdc is inconsistent
    +(see /results/f2fs/results-default/generic/556.full for details)
    ...
    (Run 'diff -u /root/xfstests/tests/generic/556.out /results/f2fs/results-default/generic/556.out.bad'  to see the entire diff)
Ran: generic/556
Failures: generic/556
Failed 1 of 1 tests