Change IoVecBuffer[Mut] len to u32

Signed-off-by: Brandon Pike <bpike@amazon.com>

src/vmm/src/devices/virtio/iovec.rs

@@ -18,6 +18,8 @@ pub enum IoVecError {
     WriteOnlyDescriptor,
     /// Tried to create an 'IoVecMut` from a read-only descriptor chain
     ReadOnlyDescriptor,
+    /// Tried to create an `IoVec` or `IoVecMut` from a descriptor chain that was too large
+    OverflowedDescriptor,
     /// Guest memory error: {0}
     GuestMemory(#[from] GuestMemoryError),
 }
@@ -40,14 +42,14 @@ pub struct IoVecBuffer {
     // container of the memory regions included in this IO vector
     vecs: IoVecVec,
     // Total length of the IoVecBuffer
-    len: usize,
+    len: u32,
 }
 
 impl IoVecBuffer {
     /// Create an `IoVecBuffer` from a `DescriptorChain`
     pub fn from_descriptor_chain(head: DescriptorChain) -> Result<Self, IoVecError> {
         let mut vecs = IoVecVec::new();
-        let mut len = 0usize;
+        let mut len = 0u32;
 
         let mut next_descriptor = Some(head);
         while let Some(desc) = next_descriptor {
@@ -68,7 +70,9 @@ impl IoVecBuffer {
                 iov_base,
                 iov_len: desc.len as size_t,
             });
-            len += desc.len as usize;
+            len = len
+                .checked_add(desc.len)
+                .ok_or(IoVecError::OverflowedDescriptor)?;
 
             next_descriptor = desc.next_descriptor();
         }
@@ -77,7 +81,7 @@ impl IoVecBuffer {
     }
 
     /// Get the total length of the memory regions covered by this `IoVecBuffer`
-    pub(crate) fn len(&self) -> usize {
+    pub(crate) fn len(&self) -> u32 {
         self.len
     }
 
@@ -106,7 +110,7 @@ impl IoVecBuffer {
         mut buf: &mut [u8],
         offset: usize,
     ) -> Result<(), VolatileMemoryError> {
-        if offset < self.len() {
+        if offset < self.len() as usize {
             let expected = buf.len();
             let bytes_read = self.read_volatile_at(&mut buf, offset, expected)?;
 
@@ -188,14 +192,14 @@ pub struct IoVecBufferMut {
     // container of the memory regions included in this IO vector
     vecs: IoVecVec,
     // Total length of the IoVecBufferMut
-    len: usize,
+    len: u32,
 }
 
 impl IoVecBufferMut {
     /// Create an `IoVecBufferMut` from a `DescriptorChain`
     pub fn from_descriptor_chain(head: DescriptorChain) -> Result<Self, IoVecError> {
         let mut vecs = IoVecVec::new();
-        let mut len = 0usize;
+        let mut len = 0u32;
 
         for desc in head {
             if !desc.is_write_only() {
@@ -217,14 +221,16 @@ impl IoVecBufferMut {
                 iov_base,
                 iov_len: desc.len as size_t,
             });
-            len += desc.len as usize;
+            len = len
+                .checked_add(desc.len)
+                .ok_or(IoVecError::OverflowedDescriptor)?;
         }
 
         Ok(Self { vecs, len })
     }
 
     /// Get the total length of the memory regions covered by this `IoVecBuffer`
-    pub(crate) fn len(&self) -> usize {
+    pub(crate) fn len(&self) -> u32 {
         self.len
     }
 
@@ -244,7 +250,7 @@ impl IoVecBufferMut {
         mut buf: &[u8],
         offset: usize,
     ) -> Result<(), VolatileMemoryError> {
-        if offset < self.len() {
+        if offset < self.len() as usize {
             let expected = buf.len();
             let bytes_written = self.write_volatile_at(&mut buf, offset, expected)?;
 

src/vmm/src/devices/virtio/net/device.rs

@@ -462,7 +462,7 @@ impl Net {
 
         if let Some(ns) = mmds_ns {
             if ns.is_mmds_frame(headers) {
-                let mut frame = vec![0u8; frame_iovec.len() - vnet_hdr_len()];
+                let mut frame = vec![0u8; frame_iovec.len() as usize - vnet_hdr_len()];
                 // Ok to unwrap here, because we are passing a buffer that has the exact size
                 // of the `IoVecBuffer` minus the VNET headers.
                 frame_iovec
@@ -609,7 +609,7 @@ impl Net {
             };
 
             // We only handle frames that are up to MAX_BUFFER_SIZE
-            if buffer.len() > MAX_BUFFER_SIZE {
+            if buffer.len() as usize > MAX_BUFFER_SIZE {
                 error!("net: received too big frame from driver");
                 self.metrics.tx_malformed_frames.inc();
                 tx_queue

src/vmm/src/devices/virtio/rng/device.rs

@@ -112,7 +112,7 @@ impl Entropy {
             return Ok(0);
         }
 
-        let mut rand_bytes = vec![0; iovec.len()];
+        let mut rand_bytes = vec![0; iovec.len() as usize];
         rand::fill(&mut rand_bytes).map_err(|err| {
             METRICS.host_rng_fails.inc();
             err

src/vmm/src/devices/virtio/vsock/csm/connection.rs

@@ -216,7 +216,7 @@ where
 
             // The maximum amount of data we can read in is limited by both the RX buffer size and
             // the peer available buffer space.
-            let max_len = std::cmp::min(pkt.buf_size(), self.peer_avail_credit());
+            let max_len = std::cmp::min(pkt.buf_size() as usize, self.peer_avail_credit());
 
             // Read data from the stream straight to the RX buffer, for maximum throughput.
             match pkt.read_at_offset_from(&mut self.stream, 0, max_len) {

src/vmm/src/devices/virtio/vsock/mod.rs

@@ -110,7 +110,7 @@ mod defs {
 #[rustfmt::skip]
 pub enum VsockError {
     /** The total length of the descriptor chain ({0}) is too short to hold a packet of length {1} + header */
-    DescChainTooShortForPacket(usize, u32),
+    DescChainTooShortForPacket(u32, u32),
     /// Empty queue
     EmptyQueue,
     /// EventFd error: {0}
@@ -122,6 +122,8 @@ pub enum VsockError {
     /** The total length of the descriptor chain ({0}) is less than the number of bytes required\
     to hold a vsock packet header.*/
     DescChainTooShortForHeader(usize),
+    /// The descriptor chain length was greater than the max ([u32::MAX])
+    DescChainOverflow,
     /// The vsock header `len` field holds an invalid value: {0}
     InvalidPktLen(u32),
     /// A data fetch was attempted when no data was available.
@@ -144,6 +146,7 @@ impl From<IoVecError> for VsockError {
             IoVecError::WriteOnlyDescriptor => VsockError::UnreadableDescriptor,
             IoVecError::ReadOnlyDescriptor => VsockError::UnwritableDescriptor,
             IoVecError::GuestMemory(err) => VsockError::GuestMemoryMmap(err),
+            IoVecError::OverflowedDescriptor => VsockError::DescChainOverflow,
         }
     }
 }

src/vmm/src/devices/virtio/vsock/packet.rs

@@ -139,7 +139,7 @@ impl VsockPacket {
             return Err(VsockError::InvalidPktLen(hdr.len));
         }
 
-        if (hdr.len as usize) > buffer.len() - VSOCK_PKT_HDR_SIZE as usize {
+        if (hdr.len) > buffer.len() - VSOCK_PKT_HDR_SIZE {
             return Err(VsockError::DescChainTooShortForPacket(
                 buffer.len(),
                 hdr.len,
@@ -160,8 +160,8 @@ impl VsockPacket {
     pub fn from_rx_virtq_head(chain: DescriptorChain) -> Result<Self, VsockError> {
         let buffer = IoVecBufferMut::from_descriptor_chain(chain)?;
 
-        if buffer.len() < VSOCK_PKT_HDR_SIZE as usize {
-            return Err(VsockError::DescChainTooShortForHeader(buffer.len()));
+        if buffer.len() < VSOCK_PKT_HDR_SIZE {
+            return Err(VsockError::DescChainTooShortForHeader(buffer.len() as usize));
         }
 
         Ok(Self {
@@ -212,7 +212,7 @@ impl VsockPacket {
             VsockPacketBuffer::Tx(ref iovec_buf) => iovec_buf.len(),
             VsockPacketBuffer::Rx(ref iovec_buf) => iovec_buf.len(),
         };
-        chain_length - VSOCK_PKT_HDR_SIZE as usize
+        (chain_length - VSOCK_PKT_HDR_SIZE) as usize
     }
 
     pub fn read_at_offset_from<T: ReadVolatile + Debug>(
@@ -225,8 +225,7 @@ impl VsockPacket {
             VsockPacketBuffer::Tx(_) => Err(VsockError::UnwritableDescriptor),
             VsockPacketBuffer::Rx(ref mut buffer) => {
                 if count
-                    > buffer
-                        .len()
+                    > (buffer.len() as usize)
                         .saturating_sub(VSOCK_PKT_HDR_SIZE as usize)
                         .saturating_sub(offset)
                 {
@@ -249,8 +248,7 @@ impl VsockPacket {
         match self.buffer {
             VsockPacketBuffer::Tx(ref buffer) => {
                 if count
-                    > buffer
-                        .len()
+                    > (buffer.len() as usize)
                         .saturating_sub(VSOCK_PKT_HDR_SIZE as usize)
                         .saturating_sub(offset)
                 {
@@ -427,10 +425,7 @@ mod tests {
                     .unwrap(),
             )
             .unwrap();
-            assert_eq!(
-                pkt.buf_size(),
-                handler_ctx.guest_txvq.dtable[1].len.get() as usize
-            );
+            assert_eq!(pkt.buf_size(), handler_ctx.guest_txvq.dtable[1].len.get());
         }
 
         // Test case: error on write-only hdr descriptor.