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Message-ID: <6a7591c133208a11b24169ed74124dca3c11c7fe.camel@kernel.org>
Subject: Re: [PATCH 0/2] ceph: fscrypt: fix atomic open bug for encrypted
 directories
From:   Jeff Layton <jlayton@kernel.org>
To:     =?ISO-8859-1?Q?Lu=EDs?= Henriques <lhenriques@suse.de>,
        Eric Biggers <ebiggers@kernel.org>,
        Xiubo Li <xiubli@redhat.com>
Cc:     "Theodore Y. Ts'o" <tytso@mit.edu>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        Ilya Dryomov <idryomov@gmail.com>,
        linux-fscrypt@vger.kernel.org, ceph-devel@vger.kernel.org,
        linux-kernel@vger.kernel.org
Date:   Mon, 13 Mar 2023 13:11:57 -0400
In-Reply-To: <20230313123310.13040-1-lhenriques@suse.de>
References: <20230313123310.13040-1-lhenriques@suse.de>
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On Mon, 2023-03-13 at 12:33 +0000, Lu=EDs Henriques wrote:
> Hi!
>=20
> I started seeing fstest generic/123 failing in ceph fscrypt, when running=
 it
> with 'test_dummy_encryption'.  This test is quite simple:
>=20
> 1. Creates a directory with write permissions for root only
> 2. Writes into a file in that directory
> 3. Uses 'su' to try to modify that file as a different user, and
>    gets -EPERM
>=20
> All the test steps succeed, but the test fails to cleanup: 'rm -rf <dir>'
> will fail with -ENOTEMPTY.  'strace' shows that calling unlinkat() to rem=
ove
> the file got a -ENOENT and then -ENOTEMPTY for the directory.
>=20
> This is because 'su' does a drop_caches ('su (874): drop_caches: 2' in
> dmesg), and ceph's atomic open will do:
>=20
> 	if (IS_ENCRYPTED(dir)) {
> 		set_bit(CEPH_MDS_R_FSCRYPT_FILE, &req->r_req_flags);
> 		if (!fscrypt_has_encryption_key(dir)) {
> 			spin_lock(&dentry->d_lock);
> 			dentry->d_flags |=3D DCACHE_NOKEY_NAME;
> 			spin_unlock(&dentry->d_lock);
> 		}
> 	}
>=20
> Although 'dir' has the encryption key available, fscrypt_has_encryption_k=
ey()
> will return 'false' because fscrypt info isn't yet set after the cache
> cleanup.
>=20
> The first patch will add a new helper for the atomic_open that will force
> the fscrypt info to be loaded into an inode that has been evicted recentl=
y
> but for which the key is still available.
>=20
> The second patch switches ceph atomic_open to use the new fscrypt helper.
>=20
> Cheers,
> --
> Lu=EDs
>=20
> Changes since initial RFC (after Eric's review):
> - Added kerneldoc comments to the new fscrypt helper
> - Dropped '__' from helper name (now fscrypt_prepare_atomic_open())
> - Added IS_ENCRYPTED() check in helper
> - DCACHE_NOKEY_NAME is not set if fscrypt_get_encryption_info() returns a=
n
>   error
> - Fixed helper for !CONFIG_FS_ENCRYPTION (now defined 'static inline')
>=20
> Lu=EDs Henriques (2):
>   fscrypt: new helper function - fscrypt_prepare_atomic_open()
>   ceph: switch atomic open to use new fscrypt helper
>=20
>  fs/ceph/file.c          |  8 +++-----
>  fs/crypto/hooks.c       | 35 +++++++++++++++++++++++++++++++++++
>  include/linux/fscrypt.h |  7 +++++++
>  3 files changed, 45 insertions(+), 5 deletions(-)
>=20

Looks like a nice cleanup.

Reviewed-by: Jeff Layton <jlayton@kernel.org>