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>

1 files changed, 2 insertions, 3 deletions

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);