fscrypto: make filename crypto functions return 0 on success

Several filename crypto functions: fname_decrypt(),
fscrypt_fname_disk_to_usr(), and fscrypt_fname_usr_to_disk(), returned
the output length on success or -errno on failure.  However, the output
length was redundant with the value written to 'oname->len'.  It is also
potentially error-prone to make callers have to check for '< 0' instead
of '!= 0'.

Therefore, make these functions return 0 instead of a length, and make
the callers who cared about the return value being a length use
'oname->len' instead.  For consistency also make other callers check for
a nonzero result rather than a negative result.

This change also fixes the inconsistency of fname_encrypt() actually
already returning 0 on success, not a length like the other filename
crypto functions and as documented in its function comment.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Acked-by: Jaegeuk Kim <jaegeuk@kernel.org>

3 files changed, 9 insertions, 9 deletions

diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index 67415e0e6af0..4d4b91029109 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -260,11 +260,12 @@ static int ext4_readdir(struct file *file, struct dir_context *ctx)
                                         /* Directory is encrypted */
                                         err = fscrypt_fname_disk_to_usr(inode,
                                                 0, 0, &de_name, &fstr);
+                                        de_name = fstr;
                                         fstr.len = save_len;
-                                        if (err < 0)
+                                        if (err)
                                                 goto errout;
                                         if (!dir_emit(ctx,
-                                            fstr.name, err,
+                                            de_name.name, de_name.len,
                                             le32_to_cpu(de->inode),
                                             get_dtype(sb, de->file_type)))
                                                 goto done;
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 34c0142caf6a..2243ae2ad2ee 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -639,7 +639,7 @@ static struct stats dx_show_leaf(struct inode *dir,
                                         res = fscrypt_fname_alloc_buffer(
                                                 dir, len,
                                                 &fname_crypto_str);
-                                        if (res < 0)
+                                        if (res)
                                                 printk(KERN_WARNING "Error "
                                                         "allocating crypto "
                                                         "buffer--skipping "
@@ -647,7 +647,7 @@ static struct stats dx_show_leaf(struct inode *dir,
                                         res = fscrypt_fname_disk_to_usr(dir,
                                                 0, 0, &de_name,
                                                 &fname_crypto_str);
-                                        if (res < 0) {
+                                        if (res) {
                                                 printk(KERN_WARNING "Error "
                                                         "converting filename "
                                                         "from disk to usr"
@@ -1011,7 +1011,7 @@ static int htree_dirblock_to_tree(struct file *dir_file,
                         err = fscrypt_fname_disk_to_usr(dir, hinfo->hash,
                                         hinfo->minor_hash, &de_name,
                                         &fname_crypto_str);
-                        if (err < 0) {
+                        if (err) {
                                 count = err;
                                 goto errout;
                         }
@@ -3144,7 +3144,7 @@ static int ext4_symlink(struct inode *dir,
                 istr.name = (const unsigned char *) symname;
                 istr.len = len;
                 err = fscrypt_fname_usr_to_disk(inode, &istr, &ostr);
-                if (err < 0)
+                if (err)
                         goto err_drop_inode;
                 sd->len = cpu_to_le16(ostr.len);
                 disk_link.name = (char *) sd;
diff --git a/fs/ext4/symlink.c b/fs/ext4/symlink.c
index 04a7850a0d45..0a26cbd529c8 100644
--- a/fs/ext4/symlink.c
+++ b/fs/ext4/symlink.c
@@ -68,12 +68,11 @@ static const char *ext4_encrypted_get_link(struct dentry *dentry,
         paddr = pstr.name;
 
         res = fscrypt_fname_disk_to_usr(inode, 0, 0, &cstr, &pstr);
-        if (res < 0)
+        if (res)
                 goto errout;
 
         /* Null-terminate the name */
-        if (res <= pstr.len)
-                paddr[res] = '\0';
+        paddr[pstr.len] = '\0';
         if (cpage)
                 put_page(cpage);
         set_delayed_call(done, kfree_link, paddr);