ksmbd: fix potential double free on smb2_read_pipe() error path

Fix new smatch warnings:
fs/smb/server/smb2pdu.c:6131 smb2_read_pipe() error: double free of 'rpc_resp'

Fixes: e2b76ab8 ("ksmbd: add support for read compound")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/server/smb2pdu.c

@@ -6152,12 +6152,12 @@ static noinline int smb2_read_pipe(struct ksmbd_work *work)
 		memcpy(aux_payload_buf, rpc_resp->payload, rpc_resp->payload_sz);
 
 		nbytes = rpc_resp->payload_sz;
-		kvfree(rpc_resp);
 		err = ksmbd_iov_pin_rsp_read(work, (void *)rsp,
 					     offsetof(struct smb2_read_rsp, Buffer),
 					     aux_payload_buf, nbytes);
 		if (err)
 			goto out;
+		kvfree(rpc_resp);
 	} else {
 		err = ksmbd_iov_pin_rsp(work, (void *)rsp,
 					offsetof(struct smb2_read_rsp, Buffer));