fscrypt: introduce fscrypt_prepare_readdir()

The last remaining use of fscrypt_get_encryption_info() from filesystems
is for readdir (->iterate_shared()).  Every other call is now in
fs/crypto/ as part of some other higher-level operation.

We need to add a new argument to fscrypt_get_encryption_info() to
indicate whether the encryption policy is allowed to be unrecognized or
not.  Doing this is easier if we can work with high-level operations
rather than direct filesystem use of fscrypt_get_encryption_info().

So add a function fscrypt_prepare_readdir() which wraps the call to
fscrypt_get_encryption_info() for the readdir use case.

Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20201203022041.230976-6-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c
index c809a4a..82f351d 100644 (file)
--- a/fs/crypto/hooks.c
+++ b/fs/crypto/hooks.c
@@ -114,6 +114,12 @@ int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry,
 }
 EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup);
 
+int __fscrypt_prepare_readdir(struct inode *dir)
+{
+       return fscrypt_get_encryption_info(dir);
+}
+EXPORT_SYMBOL_GPL(__fscrypt_prepare_readdir);
+
 /**
  * fscrypt_prepare_setflags() - prepare to change flags with FS_IOC_SETFLAGS
  * @inode: the inode on which flags are being changed

diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index 16bfbdd..c6d1635 100644 (file)
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -118,11 +118,9 @@ static int ext4_readdir(struct file *file, struct dir_context *ctx)
        struct buffer_head *bh = NULL;
        struct fscrypt_str fstr = FSTR_INIT(NULL, 0);
 
-       if (IS_ENCRYPTED(inode)) {
-               err = fscrypt_get_encryption_info(inode);
-               if (err)
-                       return err;
-       }
+       err = fscrypt_prepare_readdir(inode);
+       if (err)
+               return err;
 
        if (is_dx_dir(inode)) {
                err = ext4_dx_readdir(file, ctx);

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 7b31aea..5fa8436 100644 (file)
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1004,7 +1004,7 @@ static int htree_dirblock_to_tree(struct file *dir_file,
                                           EXT4_DIR_REC_LEN(0));
        /* Check if the directory is encrypted */
        if (IS_ENCRYPTED(dir)) {
-               err = fscrypt_get_encryption_info(dir);
+               err = fscrypt_prepare_readdir(dir);
                if (err < 0) {
                        brelse(bh);
                        return err;

diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index 47bee95..049500f 100644 (file)
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -1022,7 +1022,7 @@ static int f2fs_readdir(struct file *file, struct dir_context *ctx)
        int err = 0;
 
        if (IS_ENCRYPTED(inode)) {
-               err = fscrypt_get_encryption_info(inode);
+               err = fscrypt_prepare_readdir(inode);
                if (err)
                        goto out;
 

diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index 009fbf8..1f33a55 100644 (file)
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -514,7 +514,7 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx)
                return 0;
 
        if (encrypted) {
-               err = fscrypt_get_encryption_info(dir);
+               err = fscrypt_prepare_readdir(dir);
                if (err)
                        return err;
 

diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index 0c9e649..8cbb26f 100644 (file)
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -242,6 +242,7 @@ int __fscrypt_prepare_rename(struct inode *old_dir, struct dentry *old_dentry,
                             unsigned int flags);
 int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry,
                             struct fscrypt_name *fname);
+int __fscrypt_prepare_readdir(struct inode *dir);
 int fscrypt_prepare_setflags(struct inode *inode,
                             unsigned int oldflags, unsigned int flags);
 int fscrypt_prepare_symlink(struct inode *dir, const char *target,
@@ -537,6 +538,11 @@ static inline int __fscrypt_prepare_lookup(struct inode *dir,
        return -EOPNOTSUPP;
 }
 
+static inline int __fscrypt_prepare_readdir(struct inode *dir)
+{
+       return -EOPNOTSUPP;
+}
+
 static inline int fscrypt_prepare_setflags(struct inode *inode,
                                           unsigned int oldflags,
                                           unsigned int flags)
@@ -796,6 +802,24 @@ static inline int fscrypt_prepare_lookup(struct inode *dir,
 }
 
 /**
+ * fscrypt_prepare_readdir() - prepare to read a possibly-encrypted directory
+ * @dir: the directory inode
+ *
+ * If the directory is encrypted and it doesn't already have its encryption key
+ * set up, try to set it up so that the filenames will be listed in plaintext
+ * form rather than in no-key form.
+ *
+ * Return: 0 on success; -errno on error.  Note that the encryption key being
+ *        unavailable is not considered an error.
+ */
+static inline int fscrypt_prepare_readdir(struct inode *dir)
+{
+       if (IS_ENCRYPTED(dir))
+               return __fscrypt_prepare_readdir(dir);
+       return 0;
+}
+
+/**
  * fscrypt_prepare_setattr() - prepare to change a possibly-encrypted inode's
  *                            attributes
  * @dentry: dentry through which the inode is being changed