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Ts'o" , Jaegeuk Kim , Ilya Dryomov , linux-fscrypt@vger.kernel.org, ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org, =?utf-8?q?Lu?= =?utf-8?q?=C3=ADs_Henriques?= Subject: [PATCH v3 0/3] ceph: fscrypt: fix atomic open bug for encrypted directories Date: Thu, 16 Mar 2023 18:14:10 +0000 Message-Id: <20230316181413.26916-1-lhenriques@suse.de> MIME-Version: 1.0 X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1760550762725495698?= X-GMAIL-MSGID: =?utf-8?q?1760550762725495698?= Hi! I started seeing fstest generic/123 failing in ceph fscrypt, when running it with 'test_dummy_encryption'. This test is quite simple: 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 All the test steps succeed, but the test fails to cleanup: 'rm -rf ' will fail with -ENOTEMPTY. 'strace' shows that calling unlinkat() to remove the file got a -ENOENT and then -ENOTEMPTY for the directory. This is because 'su' does a drop_caches ('su (874): drop_caches: 2' in dmesg), and ceph's atomic open will do: 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 |= DCACHE_NOKEY_NAME; spin_unlock(&dentry->d_lock); } } Although 'dir' has the encryption key available, fscrypt_has_encryption_key() will return 'false' because fscrypt info isn't yet set after the cache cleanup. 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 recently but for which the key is still available. The second patch switches ceph atomic_open to use the new fscrypt helper. Cheers, Tested-by: Xiubo Li and Reviewed-by: Xiubo Li --- Luís Changes since v2: - Make helper more generic and to be used both in lookup and atomic open operations - Modify ceph_lookup (patch 0002) and ceph_atomic_open (patch 0003) to use the new helper Changes since v1: - Dropped IS_ENCRYPTED() from helper function because kerneldoc says already that it applies to encrypted directories and, most importantly, because it would introduce a different behaviour for CONFIG_FS_ENCRYPTION and !CONFIG_FS_ENCRYPTION. - Rephrased helper kerneldoc 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 an error - Fixed helper for !CONFIG_FS_ENCRYPTION (now defined 'static inline') Luís Henriques (3): fscrypt: new helper function - fscrypt_prepare_lookup_partial() ceph: switch ceph_open() to use new fscrypt helper ceph: switch ceph_open_atomic() to use the new fscrypt helper fs/ceph/dir.c | 13 +++++++------ fs/ceph/file.c | 8 +++----- fs/crypto/hooks.c | 37 +++++++++++++++++++++++++++++++++++++ include/linux/fscrypt.h | 7 +++++++ 4 files changed, 54 insertions(+), 11 deletions(-)