1 files changed, 39 insertions, 8 deletions

diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
index a9be4bc74a94..12bd61d20f69 100644
--- a/fs/crypto/fname.c
+++ b/fs/crypto/fname.c
@@ -19,6 +19,13 @@
 #include "fscrypt_private.h"
 
 /*
+ * The minimum message length (input and output length), in bytes, for all
+ * filenames encryption modes.  Filenames shorter than this will be zero-padded
+ * before being encrypted.
+ */
+#define FSCRYPT_FNAME_MIN_MSG_LEN 16
+
+/*
  * struct fscrypt_nokey_name - identifier for directory entry when key is absent
  *
  * When userspace lists an encrypted directory without access to the key, the
@@ -79,7 +86,8 @@ static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
 /**
  * fscrypt_fname_encrypt() - encrypt a filename
  * @inode: inode of the parent directory (for regular filenames)
- *	   or of the symlink (for symlink targets)
+ *	   or of the symlink (for symlink targets). Key must already be
+ *	   set up.
  * @iname: the filename to encrypt
  * @out: (output) the encrypted filename
  * @olen: size of the encrypted filename.  It must be at least @iname->len.
@@ -130,6 +138,7 @@ int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname,
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(fscrypt_fname_encrypt);
 
 /**
  * fname_decrypt() - decrypt a filename
@@ -257,9 +266,9 @@ static int fscrypt_base64url_decode(const char *src, int srclen, u8 *dst)
 	return bp - dst;
 }
 
-bool fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
-				  u32 orig_len, u32 max_len,
-				  u32 *encrypted_len_ret)
+bool __fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
+				    u32 orig_len, u32 max_len,
+				    u32 *encrypted_len_ret)
 {
 	int padding = 4 << (fscrypt_policy_flags(policy) &
 			    FSCRYPT_POLICY_FLAGS_PAD_MASK);
@@ -267,13 +276,36 @@ bool fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
 
 	if (orig_len > max_len)
 		return false;
-	encrypted_len = max(orig_len, (u32)FS_CRYPTO_BLOCK_SIZE);
+	encrypted_len = max_t(u32, orig_len, FSCRYPT_FNAME_MIN_MSG_LEN);
 	encrypted_len = round_up(encrypted_len, padding);
 	*encrypted_len_ret = min(encrypted_len, max_len);
 	return true;
 }
 
 /**
+ * fscrypt_fname_encrypted_size() - calculate length of encrypted filename
+ * @inode:		parent inode of dentry name being encrypted. Key must
+ *			already be set up.
+ * @orig_len:		length of the original filename
+ * @max_len:		maximum length to return
+ * @encrypted_len_ret:	where calculated length should be returned (on success)
+ *
+ * Filenames that are shorter than the maximum length may have their lengths
+ * increased slightly by encryption, due to padding that is applied.
+ *
+ * Return: false if the orig_len is greater than max_len. Otherwise, true and
+ *	   fill out encrypted_len_ret with the length (up to max_len).
+ */
+bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
+				  u32 max_len, u32 *encrypted_len_ret)
+{
+	return __fscrypt_fname_encrypted_size(&inode->i_crypt_info->ci_policy,
+					      orig_len, max_len,
+					      encrypted_len_ret);
+}
+EXPORT_SYMBOL_GPL(fscrypt_fname_encrypted_size);
+
+/**
  * fscrypt_fname_alloc_buffer() - allocate a buffer for presented filenames
  * @max_encrypted_len: maximum length of encrypted filenames the buffer will be
  *		       used to present
@@ -350,7 +382,7 @@ int fscrypt_fname_disk_to_usr(const struct inode *inode,
 		return 0;
 	}
 
-	if (iname->len < FS_CRYPTO_BLOCK_SIZE)
+	if (iname->len < FSCRYPT_FNAME_MIN_MSG_LEN)
 		return -EUCLEAN;
 
 	if (fscrypt_has_encryption_key(inode))
@@ -428,8 +460,7 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
 		return ret;
 
 	if (fscrypt_has_encryption_key(dir)) {
-		if (!fscrypt_fname_encrypted_size(&dir->i_crypt_info->ci_policy,
-						  iname->len, NAME_MAX,
+		if (!fscrypt_fname_encrypted_size(dir, iname->len, NAME_MAX,
 						  &fname->crypto_buf.len))
 			return -ENAMETOOLONG;
 		fname->crypto_buf.name = kmalloc(fname->crypto_buf.len,