ksmbd: fix a missing return value check bug

In the smb2_send_interim_resp(), if ksmbd_alloc_work_struct()
fails to allocate a node, it returns a NULL pointer to the
in_work pointer. This can lead to an illegal memory write of
in_work->response_buf when allocate_interim_rsp_buf() attempts
to perform a kzalloc() on it.

To address this issue, incorporating a check for the return
value of ksmbd_alloc_work_struct() ensures that the function
returns immediately upon allocation failure, thereby preventing
the aforementioned illegal memory access.

Fixes: 041bba4414cd ("ksmbd: fix wrong interim response on compound")
Signed-off-by: Wentao Liang <[email protected]>
Signed-off-by: Namjae Jeon <[email protected]>

smb2pdu.c

@@ -701,6 +701,9 @@ void smb2_send_interim_resp(struct ksmbd_work *work, __le32 status)
 	struct smb2_hdr *rsp_hdr;
 	struct ksmbd_work *in_work = ksmbd_alloc_work_struct();
 
+	if (!in_work)
+		return;
+
 	if (allocate_interim_rsp_buf(in_work)) {
 		pr_err("smb_allocate_rsp_buf failed!\n");
 		ksmbd_free_work_struct(in_work);