ksmbd: fix integer overflows on 32 bit systems

On 32bit systems the addition operations in ipc_msg_alloc() can
potentially overflow leading to memory corruption.
Add bounds checking using KSMBD_IPC_MAX_PAYLOAD to avoid overflow.

Fixes: 0626e66 ("cifsd: add server handler for central processing and tranport layers")
Cc: stable@vger.kernel.org
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: Dan Carpenter

fs/smb/server/transport_ipc.c

@@ -627,6 +627,9 @@ ksmbd_ipc_spnego_authen_request(const char *spnego_blob, int blob_len)
 	struct ksmbd_spnego_authen_request *req;
 	struct ksmbd_spnego_authen_response *resp;
 
+	if (blob_len > KSMBD_IPC_MAX_PAYLOAD)
+		return NULL;
+
 	msg = ipc_msg_alloc(sizeof(struct ksmbd_spnego_authen_request) +
 			blob_len + 1);
 	if (!msg)
@@ -806,6 +809,9 @@ struct ksmbd_rpc_command *ksmbd_rpc_write(struct ksmbd_session *sess, int handle
 	struct ksmbd_rpc_command *req;
 	struct ksmbd_rpc_command *resp;
 
+	if (payload_sz > KSMBD_IPC_MAX_PAYLOAD)
+		return NULL;
+
 	msg = ipc_msg_alloc(sizeof(struct ksmbd_rpc_command) + payload_sz + 1);
 	if (!msg)
 		return NULL;
@@ -854,6 +860,9 @@ struct ksmbd_rpc_command *ksmbd_rpc_ioctl(struct ksmbd_session *sess, int handle
 	struct ksmbd_rpc_command *req;
 	struct ksmbd_rpc_command *resp;
 
+	if (payload_sz > KSMBD_IPC_MAX_PAYLOAD)
+		return NULL;
+
 	msg = ipc_msg_alloc(sizeof(struct ksmbd_rpc_command) + payload_sz + 1);
 	if (!msg)
 		return NULL;