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>

diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
index 6bbc3b1..90697c7 100644 (file)
--- a/fs/crypto/fname.c
+++ b/fs/crypto/fname.c
@@ -35,11 +35,11 @@ static void fname_crypt_complete(struct crypto_async_request *req, int res)
 }
 
 /**
- * fname_encrypt() -
+ * fname_encrypt() - encrypt a filename
  *
- * This function encrypts the input filename, and returns the length of the
- * ciphertext. Errors are returned as negative numbers.  We trust the caller to
- * allocate sufficient memory to oname string.
+ * The caller must have allocated sufficient memory for the @oname string.
+ *
+ * Return: 0 on success, -errno on failure
  */
 static int fname_encrypt(struct inode *inode,
                        const struct qstr *iname, struct fscrypt_str *oname)
@@ -105,20 +105,22 @@ static int fname_encrypt(struct inode *inode,
        }
        kfree(alloc_buf);
        skcipher_request_free(req);
-       if (res < 0)
+       if (res < 0) {
                printk_ratelimited(KERN_ERR
                                "%s: Error (error code %d)\n", __func__, res);
+               return res;
+       }
 
        oname->len = ciphertext_len;
-       return res;
+       return 0;
 }
 
-/*
- * fname_decrypt()
- *     This function decrypts the input filename, and returns
- *     the length of the plaintext.
- *     Errors are returned as negative numbers.
- *     We trust the caller to allocate sufficient memory to oname string.
+/**
+ * fname_decrypt() - decrypt a filename
+ *
+ * The caller must have allocated sufficient memory for the @oname string.
+ *
+ * Return: 0 on success, -errno on failure
  */
 static int fname_decrypt(struct inode *inode,
                                const struct fscrypt_str *iname,
@@ -168,7 +170,7 @@ static int fname_decrypt(struct inode *inode,
        }
 
        oname->len = strnlen(oname->name, iname->len);
-       return oname->len;
+       return 0;
 }
 
 static const char *lookup_table =
@@ -279,6 +281,10 @@ EXPORT_SYMBOL(fscrypt_fname_free_buffer);
 /**
  * fscrypt_fname_disk_to_usr() - converts a filename from disk space to user
  * space
+ *
+ * The caller must have allocated sufficient memory for the @oname string.
+ *
+ * Return: 0 on success, -errno on failure
  */
 int fscrypt_fname_disk_to_usr(struct inode *inode,
                        u32 hash, u32 minor_hash,
@@ -287,13 +293,12 @@ int fscrypt_fname_disk_to_usr(struct inode *inode,
 {
        const struct qstr qname = FSTR_TO_QSTR(iname);
        char buf[24];
-       int ret;
 
        if (fscrypt_is_dot_dotdot(&qname)) {
                oname->name[0] = '.';
                oname->name[iname->len - 1] = '.';
                oname->len = iname->len;
-               return oname->len;
+               return 0;
        }
 
        if (iname->len < FS_CRYPTO_BLOCK_SIZE)
@@ -303,9 +308,9 @@ int fscrypt_fname_disk_to_usr(struct inode *inode,
                return fname_decrypt(inode, iname, oname);
 
        if (iname->len <= FS_FNAME_CRYPTO_DIGEST_SIZE) {
-               ret = digest_encode(iname->name, iname->len, oname->name);
-               oname->len = ret;
-               return ret;
+               oname->len = digest_encode(iname->name, iname->len,
+                                          oname->name);
+               return 0;
        }
        if (hash) {
                memcpy(buf, &hash, 4);
@@ -315,15 +320,18 @@ int fscrypt_fname_disk_to_usr(struct inode *inode,
        }
        memcpy(buf + 8, iname->name + iname->len - 16, 16);
        oname->name[0] = '_';
-       ret = digest_encode(buf, 24, oname->name + 1);
-       oname->len = ret + 1;
-       return ret + 1;
+       oname->len = 1 + digest_encode(buf, 24, oname->name + 1);
+       return 0;
 }
 EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);
 
 /**
  * fscrypt_fname_usr_to_disk() - converts a filename from user space to disk
  * space
+ *
+ * The caller must have allocated sufficient memory for the @oname string.
+ *
+ * Return: 0 on success, -errno on failure
  */
 int fscrypt_fname_usr_to_disk(struct inode *inode,
                        const struct qstr *iname,
@@ -333,7 +341,7 @@ int fscrypt_fname_usr_to_disk(struct inode *inode,
                oname->name[0] = '.';
                oname->name[iname->len - 1] = '.';
                oname->len = iname->len;
-               return oname->len;
+               return 0;
        }
        if (inode->i_crypt_info)
                return fname_encrypt(inode, iname, oname);
@@ -367,10 +375,10 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
        if (dir->i_crypt_info) {
                ret = fscrypt_fname_alloc_buffer(dir, iname->len,
                                                        &fname->crypto_buf);
-               if (ret < 0)
+               if (ret)
                        return ret;
                ret = fname_encrypt(dir, iname, &fname->crypto_buf);
-               if (ret < 0)
+               if (ret)
                        goto errout;
                fname->disk_name.name = fname->crypto_buf.name;
                fname->disk_name.len = fname->crypto_buf.len;

diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index 67415e0..4d4b910 100644 (file)
--- 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 34c0142..2243ae2 100644 (file)
--- 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 04a7850..0a26cbd 100644 (file)
--- 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);

diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index 9054aea..8716943 100644 (file)
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -786,7 +786,7 @@ bool f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d,
 
                if (f2fs_encrypted_inode(d->inode)) {
                        int save_len = fstr->len;
-                       int ret;
+                       int err;
 
                        de_name.name = f2fs_kmalloc(de_name.len, GFP_NOFS);
                        if (!de_name.name)
@@ -794,11 +794,11 @@ bool f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d,
 
                        memcpy(de_name.name, d->filename[bit_pos], de_name.len);
 
-                       ret = fscrypt_fname_disk_to_usr(d->inode,
+                       err = fscrypt_fname_disk_to_usr(d->inode,
                                                (u32)de->hash_code, 0,
                                                &de_name, fstr);
                        kfree(de_name.name);
-                       if (ret < 0)
+                       if (err)
                                return true;
 
                        de_name = *fstr;

diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
index 73fa356..afd5633 100644 (file)
--- a/fs/f2fs/namei.c
+++ b/fs/f2fs/namei.c
@@ -449,7 +449,7 @@ static int f2fs_symlink(struct inode *dir, struct dentry *dentry,
                ostr.name = sd->encrypted_path;
                ostr.len = disk_link.len;
                err = fscrypt_fname_usr_to_disk(inode, &istr, &ostr);
-               if (err < 0)
+               if (err)
                        goto err_out;
 
                sd->len = cpu_to_le16(ostr.len);
@@ -1048,7 +1048,7 @@ static const char *f2fs_encrypted_get_link(struct dentry *dentry,
                goto errout;
 
        res = fscrypt_fname_disk_to_usr(inode, 0, 0, &cstr, &pstr);
-       if (res < 0)
+       if (res)
                goto errout;
 
        /* this is broken symlink case */
@@ -1060,7 +1060,7 @@ static const char *f2fs_encrypted_get_link(struct dentry *dentry,
        paddr = pstr.name;
 
        /* Null-terminate the name */
-       paddr[res] = '\0';
+       paddr[pstr.len] = '\0';
 
        put_page(cpage);
        set_delayed_call(done, kfree_link, paddr);