diff --git a/vhost_rs/src/vhost_user/slave_req_handler.rs b/vhost_rs/src/vhost_user/slave_req_handler.rs
index 934c6d498..480689f7f 100644
--- a/vhost_rs/src/vhost_user/slave_req_handler.rs
+++ b/vhost_rs/src/vhost_user/slave_req_handler.rs
@@ -265,7 +265,6 @@ impl<S: VhostUserSlaveReqHandler> SlaveReqHandler<S> {
                 if self.acked_protocol_features & VhostUserProtocolFeatures::CONFIG.bits() == 0 {
                     return Err(Error::InvalidOperation);
                 }
-                self.check_request_size(&hdr, size, mem::size_of::<VhostUserConfig>())?;
                 self.get_config(&hdr, &buf)?;
             }
             MasterReq::SET_CONFIG => {
@@ -341,6 +340,10 @@ impl<S: VhostUserSlaveReqHandler> SlaveReqHandler<S> {
         if !msg.is_valid() {
             return Err(Error::InvalidMessage);
         }
+        let payload_offset = mem::size_of::<VhostUserConfig>();
+        if buf.len() - payload_offset != msg.size as usize {
+            return Err(Error::InvalidMessage);
+        }
         let flags = match VhostUserConfigFlags::from_bits(msg.flags) {
             Some(val) => val,
             None => return Err(Error::InvalidMessage),
@@ -519,6 +522,7 @@ impl<S: VhostUserSlaveReqHandler> SlaveReqHandler<S> {
     fn new_reply_header<T: Sized>(
         &self,
         req: &VhostUserMsgHeader<MasterReq>,
+        payload_size: usize,
     ) -> Result<VhostUserMsgHeader<MasterReq>> {
         if mem::size_of::<T>() > MAX_MSG_SIZE {
             return Err(Error::InvalidParam);
@@ -527,7 +531,7 @@ impl<S: VhostUserSlaveReqHandler> SlaveReqHandler<S> {
         Ok(VhostUserMsgHeader::new(
             req.get_code(),
             VhostUserHeaderFlag::REPLY.bits(),
-            mem::size_of::<T>() as u32,
+            (mem::size_of::<T>() + payload_size) as u32,
         ))
     }
 
@@ -537,7 +541,7 @@ impl<S: VhostUserSlaveReqHandler> SlaveReqHandler<S> {
         res: Result<()>,
     ) -> Result<()> {
         if self.reply_ack_enabled {
-            let hdr = self.new_reply_header::<VhostUserU64>(req)?;
+            let hdr = self.new_reply_header::<VhostUserU64>(req, 0)?;
             let val = match res {
                 Ok(_) => 0,
                 Err(_) => 1,
@@ -553,7 +557,7 @@ impl<S: VhostUserSlaveReqHandler> SlaveReqHandler<S> {
         req: &VhostUserMsgHeader<MasterReq>,
         msg: &T,
     ) -> Result<()> {
-        let hdr = self.new_reply_header::<T>(req)?;
+        let hdr = self.new_reply_header::<T>(req, 0)?;
         self.main_sock.send_message(&hdr, msg, None)?;
         Ok(())
     }
@@ -568,7 +572,7 @@ impl<S: VhostUserSlaveReqHandler> SlaveReqHandler<S> {
         T: Sized,
         P: Sized,
     {
-        let hdr = self.new_reply_header::<T>(req)?;
+        let hdr = self.new_reply_header::<T>(req, payload.len())?;
         self.main_sock
             .send_message_with_payload(&hdr, msg, payload, None)?;
         Ok(())
diff --git a/vhost_user_backend/src/lib.rs b/vhost_user_backend/src/lib.rs
index 3889245b2..8f34a1555 100644
--- a/vhost_user_backend/src/lib.rs
+++ b/vhost_user_backend/src/lib.rs
@@ -15,7 +15,6 @@ use std::thread;
 use vhost_rs::vhost_user::message::{
     VhostUserConfigFlags, VhostUserMemoryRegion, VhostUserProtocolFeatures,
     VhostUserVirtioFeatures, VhostUserVringAddrFlags, VhostUserVringState,
-    VHOST_USER_CONFIG_OFFSET, VHOST_USER_CONFIG_SIZE,
 };
 use vhost_rs::vhost_user::{
     Error as VhostUserError, Result as VhostUserResult, SlaveListener, VhostUserSlaveReqHandler,
@@ -720,16 +719,6 @@ impl<S: VhostUserBackend> VhostUserSlaveReqHandler for VhostUserHandler<S> {
         size: u32,
         _flags: VhostUserConfigFlags,
     ) -> VhostUserResult<Vec<u8>> {
-        if self.acked_features & VhostUserProtocolFeatures::CONFIG.bits() == 0 {
-            return Err(VhostUserError::InvalidOperation);
-        } else if offset < VHOST_USER_CONFIG_OFFSET
-            || offset >= VHOST_USER_CONFIG_SIZE
-            || size > VHOST_USER_CONFIG_SIZE - VHOST_USER_CONFIG_OFFSET
-            || size + offset > VHOST_USER_CONFIG_SIZE
-        {
-            return Err(VhostUserError::InvalidParam);
-        }
-
         Ok(self.backend.read().unwrap().get_config(offset, size))
     }
 
@@ -739,17 +728,6 @@ impl<S: VhostUserBackend> VhostUserSlaveReqHandler for VhostUserHandler<S> {
         buf: &[u8],
         _flags: VhostUserConfigFlags,
     ) -> VhostUserResult<()> {
-        let size = buf.len() as u32;
-        if self.acked_features & VhostUserProtocolFeatures::CONFIG.bits() == 0 {
-            return Err(VhostUserError::InvalidOperation);
-        } else if offset < VHOST_USER_CONFIG_OFFSET
-            || offset >= VHOST_USER_CONFIG_SIZE
-            || size > VHOST_USER_CONFIG_SIZE - VHOST_USER_CONFIG_OFFSET
-            || size + offset > VHOST_USER_CONFIG_SIZE
-        {
-            return Err(VhostUserError::InvalidParam);
-        }
-
         self.backend
             .write()
             .unwrap()