exfat: add missing brelse() calls on error paths

If the second exfat_get_dentry() call fails then we need to release
old_bh before returning.  There is a similar bug in exfat_move_file().

Fixes: 5f2aa075070c ("exfat: add inode operations")
Reported-by: Markus Elfring <Markus.Elfring@web.de>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>

Author: Dan Carpenter

namei.c

@@ -1184,10 +1184,14 @@ static int exfat_rename_file(struct inode *inode, struct exfat_chain *p_dir,
 
 		epold = exfat_get_dentry(sb, p_dir, oldentry + 1, &old_bh,
 			&sector_old);
+		if (!epold)
+			return -EIO;
 		epnew = exfat_get_dentry(sb, p_dir, newentry + 1, &new_bh,
 			&sector_new);
-		if (!epold || !epnew)
+		if (!epnew) {
+			brelse(old_bh);
 			return -EIO;
+		}
 
 		memcpy(epnew, epold, DENTRY_SIZE);
 		exfat_update_bh(sb, new_bh, sync);
@@ -1268,10 +1272,14 @@ static int exfat_move_file(struct inode *inode, struct exfat_chain *p_olddir,
 
 	epmov = exfat_get_dentry(sb, p_olddir, oldentry + 1, &mov_bh,
 		&sector_mov);
+	if (!epmov)
+		return -EIO;
 	epnew = exfat_get_dentry(sb, p_newdir, newentry + 1, &new_bh,
 		&sector_new);
-	if (!epmov || !epnew)
+	if (!epnew) {
+		brelse(mov_bh);
 		return -EIO;
+	}
 
 	memcpy(epnew, epmov, DENTRY_SIZE);
 	exfat_update_bh(sb, new_bh, IS_DIRSYNC(inode));