cifs: smb2ops: Fix NULL check in smb2_query_symlink

The current code null checks variable err_buf, which is always null
when it is checked, hence utf16_path is free'd and the function
returns -ENOENT everytime it is called, making it impossible for the
execution path to reach the following code:

err_buf = err_iov.iov_base;

Fix this by null checking err_iov.iov_base instead of err_buf. Also,
notice that err_buf no longer needs to be initialized to NULL.

Addresses-Coverity-ID: 1467876 ("Logically dead code")
Fixes: 2d636199e400 ("cifs: Change SMB2_open to return an iov for the error parameter")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>

fs/cifs/smb2ops.c

@@ -1452,7 +1452,7 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
 	struct cifs_open_parms oparms;
 	struct cifs_fid fid;
 	struct kvec err_iov = {NULL, 0};
-	struct smb2_err_rsp *err_buf = NULL;
+	struct smb2_err_rsp *err_buf;
 	struct smb2_symlink_err_rsp *symlink;
 	unsigned int sub_len;
 	unsigned int sub_offset;
@@ -1476,7 +1476,7 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
 
 	rc = SMB2_open(xid, &oparms, utf16_path, &oplock, NULL, &err_iov);
 
-	if (!rc || !err_buf) {
+	if (!rc || !err_iov.iov_base) {
 		kfree(utf16_path);
 		return -ENOENT;
 	}