[lustre-devel] [PATCH 38/50] lustre: sec: present .fscrypt in subdir mount

[James Simmons]

From: Sebastien Buisson <sbuisson at ddn.com>

fscrypt userspace tool works with a .fscrypt directory at the root of
the file system. In case of subdirectory mount, we virtually present
this .fscrypt directory at the root of the mount point so that fscrypt
can be used. This makes it possible to even do a subdirectory mount of
an encrypted directory, making clients access encrypted content only.
Internally, the .fscrypt directory is always stored at the root of
Lustre.

WC-bug-id: https://jira.whamcloud.com/browse/LU-15176
Lustre-commit: c12378fba7f0aa2f2 ("LU-15176 sec: present .fscrypt in subdir mount")
Signed-off-by: Sebastien Buisson <sbuisson at ddn.com>
Reviewed-on: https://review.whamcloud.com/46167
Reviewed-by: Patrick Farrell <pfarrell at whamcloud.com>
Reviewed-by: James Simmons <jsimmons at infradead.org>
Reviewed-by: Andreas Dilger <adilger at whamcloud.com>
Reviewed-by: Oleg Drokin <green at whamcloud.com>
Signed-off-by: James Simmons <jsimmons at infradead.org>
---
 fs/lustre/llite/crypto.c                |  9 +++++++--
 fs/lustre/llite/llite_lib.c             | 11 ++++++++++-
 fs/lustre/llite/namei.c                 |  9 +++++++++
 include/uapi/linux/lustre/lustre_user.h |  1 +
 4 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/fs/lustre/llite/crypto.c b/fs/lustre/llite/crypto.c
index f310d4c..b0e4f76 100644
--- a/fs/lustre/llite/crypto.c
+++ b/fs/lustre/llite/crypto.c
@@ -233,8 +233,13 @@ int ll_setup_filename(struct inode *dir, const struct qstr *iname,
 	}
 	rc = fscrypt_setup_filename(dir, &dname, lookup, fname);
 	if (rc == -ENOENT && lookup &&
-	    !fscrypt_has_encryption_key(dir) &&
-	    unlikely(filename_is_volatile(iname->name, iname->len, NULL))) {
+	    ((is_root_inode(dir) && iname->len == strlen(dot_fscrypt_name) &&
+	      strncmp(iname->name, dot_fscrypt_name, iname->len) == 0) ||
+	     (!fscrypt_has_encryption_key(dir) &&
+	      unlikely(filename_is_volatile(iname->name, iname->len, NULL))))) {
+		/* In case of subdir mount of an encrypted directory, we allow
+		 * lookup of /.fscrypt directory.
+		 */
 		/* For purpose of migration or mirroring without enc key, we
 		 * allow lookup of volatile file without enc context.
 		 */
diff --git a/fs/lustre/llite/llite_lib.c b/fs/lustre/llite/llite_lib.c
index 423c531..8c0a3e0 100644
--- a/fs/lustre/llite/llite_lib.c
+++ b/fs/lustre/llite/llite_lib.c
@@ -3157,7 +3157,16 @@ struct md_op_data *ll_prep_md_op_data(struct md_op_data *op_data,
 		return ERR_PTR(-ENOMEM);
 
 	ll_i2gids(op_data->op_suppgids, i1, i2);
-	op_data->op_fid1 = *ll_inode2fid(i1);
+	/* If the client is using a subdir mount and looks at what it sees as
+	 * /.fscrypt, interpret it as the .fscrypt dir at the root of the fs.
+	 */
+	if (unlikely(i1->i_sb && i1->i_sb->s_root && is_root_inode(i1) &&
+		     !fid_is_root(ll_inode2fid(i1)) &&
+		     name && namelen == strlen(dot_fscrypt_name) &&
+		     strncmp(name, dot_fscrypt_name, namelen) == 0))
+		lu_root_fid(&op_data->op_fid1);
+	else
+		op_data->op_fid1 = *ll_inode2fid(i1);
 
 	if (S_ISDIR(i1->i_mode)) {
 		down_read_non_owner(&ll_i2info(i1)->lli_lsm_sem);
diff --git a/fs/lustre/llite/namei.c b/fs/lustre/llite/namei.c
index 1e3a4fd..c05e3bf 100644
--- a/fs/lustre/llite/namei.c
+++ b/fs/lustre/llite/namei.c
@@ -2068,6 +2068,15 @@ static int ll_rename(struct inode *src, struct dentry *src_dchild,
 	if (IS_ERR(op_data))
 		return PTR_ERR(op_data);
 
+	/* If the client is using a subdir mount and does a rename to what it
+	 * sees as /.fscrypt, interpret it as the .fscrypt dir at fs root.
+	 */
+	if (unlikely(is_root_inode(tgt) && !fid_is_root(ll_inode2fid(tgt)) &&
+		     tgt_dchild->d_name.len == strlen(dot_fscrypt_name) &&
+		     strncmp(tgt_dchild->d_name.name, dot_fscrypt_name,
+			     tgt_dchild->d_name.len) == 0))
+		lu_root_fid(&op_data->op_fid2);
+
 	if (src_dchild->d_inode)
 		op_data->op_fid3 = *ll_inode2fid(src_dchild->d_inode);
 	if (tgt_dchild->d_inode)
diff --git a/include/uapi/linux/lustre/lustre_user.h b/include/uapi/linux/lustre/lustre_user.h
index 2fdd7df..96efdf0 100644
--- a/include/uapi/linux/lustre/lustre_user.h
+++ b/include/uapi/linux/lustre/lustre_user.h
@@ -1856,6 +1856,7 @@ enum ioc_data_version_flags {
 #endif
 
 #define dot_lustre_name ".lustre"
+#define dot_fscrypt_name ".fscrypt"
 
 /********* HSM **********/
 
-- 
1.8.3.1