fix nio read/write iovec bugs causing deadlock and infinite loop

Agent-Logs-Url: https://github.com/acl-dev/open-coroutine/sessions/3ee10e36-26e4-49a6-88c3-bc465b166e2f

Co-authored-by: loongs-zhang <38336731+loongs-zhang@users.noreply.github.com>

Author: Copilot

core/src/syscall/unix/mod.rs

@@ -566,8 +566,8 @@ macro_rules! impl_nio_read_iovec {
                 let mut received = 0usize;
                 let mut r = -1;
                 let mut index = 0;
-                for iovec in &vec {
-                    let mut offset = received.saturating_sub(length);
+                'outer: for iovec in &vec {
+                    let offset = received.saturating_sub(length);
                     length += iovec.iov_len;
                     if received > length {
                         index += 1;
@@ -603,11 +603,9 @@ macro_rules! impl_nio_read_iovec {
                         } else if r != -1 {
                             $crate::syscall::reset_errno();
                             received += libc::size_t::try_from(r).expect("r overflow");
-                            if received >= length {
-                                r = received.try_into().expect("received overflow");
-                                break;
-                            }
-                            offset = received.saturating_sub(length);
+                            r = received.try_into().expect("received overflow");
+                            // readv returns as soon as any data is received
+                            break 'outer;
                         }
                         let error_kind = std::io::Error::last_os_error().kind();
                         if error_kind == std::io::ErrorKind::WouldBlock {

core/src/syscall/windows/mod.rs

@@ -533,7 +533,7 @@ macro_rules! impl_nio_read_iovec {
                 let mut received = 0usize;
                 let mut r = windows_sys::Win32::Networking::WinSock::SOCKET_ERROR;
                 let mut index = 0;
-                for iovec in &vec {
+                'outer: for iovec in &vec {
                     let mut offset = received.saturating_sub(length);
                     length += iovec.len as usize;
                     if received > length {
@@ -563,13 +563,12 @@ macro_rules! impl_nio_read_iovec {
                         );
                         if r != windows_sys::Win32::Networking::WinSock::SOCKET_ERROR {
                             $crate::syscall::reset_errno();
-                            received += usize::try_from(r).expect("overflow");
-                            if received >= length {
-                                r = 0;
-                                unsafe{ $recvd.write(received.try_into().expect("overflow")) };
-                                break;
-                            }
-                            offset = received.saturating_sub(length);
+                            // WSARecv returns 0 on success; actual byte count is in *$recvd
+                            received += unsafe { *$recvd } as usize;
+                            r = 0;
+                            unsafe{ $recvd.write(received.try_into().expect("overflow")) };
+                            // WSARecv returns as soon as any data is received
+                            break 'outer;
                         }
                         let error_kind = std::io::Error::last_os_error().kind();
                         if error_kind == std::io::ErrorKind::WouldBlock {
@@ -803,7 +802,8 @@ macro_rules! impl_nio_write_iovec {
                         );
                         if r != windows_sys::Win32::Networking::WinSock::SOCKET_ERROR {
                             $crate::syscall::reset_errno();
-                            sent += usize::try_from(r).expect("overflow");
+                            // WSASend returns 0 on success; actual byte count is in *$sent
+                            sent += unsafe { *$sent } as usize;
                             if sent >= length {
                                 r = 0;
                                 unsafe{ $sent.write(sent.try_into().expect("overflow")) };