From 5cce30e20c1fc6d8463b0a99acdd9777c4ad124b Mon Sep 17 00:00:00 2001 From: database64128 Date: Mon, 9 Mar 2026 16:25:16 +0800 Subject: [PATCH] internal/poll: move rsan to heap on windows According to https://learn.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-wsarecvfrom, the memory pointed to by lpFromlen must remain available during the overlapped I/O, and therefore cannot be allocated on the stack. CL 685417 moved the rsan field out of the operation struct and placed it on stack, which violates the above requirement and causes stack corruption. Unfortunately, it is no longer possible to cleanly revert CL 685417. Instead of attempting to revert it, this CL bundles rsan together with rsa in the same sync.Pool. The new wsaRsa struct is still in the same size class, so no additional overhead is introduced by this change. Updates golang/go#77975 Updates tailscale/tailscale#18884 Updates tailscale/go#158 Cherry-picked from https://go-review.googlesource.com/c/go/+/753040 v4 Reviewed-on: https://go-review.googlesource.com/c/go/+/753040 Reviewed-by: Quim Muntal Reviewed-by: Damien Neil Change-Id: I5ffbccb332515116ddc03fb7c40ffc9293cad2ab --- src/internal/poll/fd_windows.go | 94 +++++++++++++++++++++------------ 1 file changed, 59 insertions(+), 35 deletions(-) diff --git a/src/internal/poll/fd_windows.go b/src/internal/poll/fd_windows.go index edad6563508bc6..7953ad6aac9f90 100644 --- a/src/internal/poll/fd_windows.go +++ b/src/internal/poll/fd_windows.go @@ -149,7 +149,7 @@ var wsaMsgPool = sync.Pool{ // newWSAMsg creates a new WSAMsg with the provided parameters. // Use [freeWSAMsg] to free it. -func newWSAMsg(p []byte, oob []byte, flags int, unconnected bool) *windows.WSAMsg { +func newWSAMsg(p []byte, oob []byte, flags int, rsa *wsaRsa) *windows.WSAMsg { // The returned object can't be allocated in the stack because it is accessed asynchronously // by Windows in between several system calls. If the stack frame is moved while that happens, // then Windows may access invalid memory. @@ -164,34 +164,46 @@ func newWSAMsg(p []byte, oob []byte, flags int, unconnected bool) *windows.WSAMs Buf: unsafe.SliceData(oob), } msg.Flags = uint32(flags) - if unconnected { - msg.Name = wsaRsaPool.Get().(*syscall.RawSockaddrAny) - msg.Namelen = int32(unsafe.Sizeof(syscall.RawSockaddrAny{})) + if rsa != nil { + msg.Name = &rsa.name + msg.Namelen = rsa.namelen } return msg } func freeWSAMsg(msg *windows.WSAMsg) { // Clear pointers to buffers so they can be released by garbage collector. + msg.Name = nil + msg.Namelen = 0 msg.Buffers.Len = 0 msg.Buffers.Buf = nil msg.Control.Len = 0 msg.Control.Buf = nil - if msg.Name != nil { - *msg.Name = syscall.RawSockaddrAny{} - wsaRsaPool.Put(msg.Name) - msg.Name = nil - msg.Namelen = 0 - } wsaMsgPool.Put(msg) } +// wsaRsa bundles a [syscall.RawSockaddrAny] with its length for efficient caching. +// +// When used by WSARecvFrom, wsaRsa must be on the heap. See +// https://learn.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-wsarecvfrom. +type wsaRsa struct { + name syscall.RawSockaddrAny + namelen int32 +} + var wsaRsaPool = sync.Pool{ New: func() any { - return new(syscall.RawSockaddrAny) + return new(wsaRsa) }, } +func newWSARsa() *wsaRsa { + rsa := wsaRsaPool.Get().(*wsaRsa) + rsa.name = syscall.RawSockaddrAny{} + rsa.namelen = int32(unsafe.Sizeof(syscall.RawSockaddrAny{})) + return rsa +} + var operationPool = sync.Pool{ New: func() any { return new(operation) @@ -737,19 +749,18 @@ func (fd *FD) ReadFrom(buf []byte) (int, syscall.Sockaddr, error) { fd.pin('r', &buf[0]) - rsa := wsaRsaPool.Get().(*syscall.RawSockaddrAny) + rsa := newWSARsa() defer wsaRsaPool.Put(rsa) n, err := fd.execIO('r', func(o *operation) (qty uint32, err error) { - rsan := int32(unsafe.Sizeof(*rsa)) var flags uint32 - err = syscall.WSARecvFrom(fd.Sysfd, newWsaBuf(buf), 1, &qty, &flags, rsa, &rsan, &o.o, nil) + err = syscall.WSARecvFrom(fd.Sysfd, newWsaBuf(buf), 1, &qty, &flags, &rsa.name, &rsa.namelen, &o.o, nil) return qty, err }) err = fd.eofError(n, err) if err != nil { return n, nil, err } - sa, _ := rsa.Sockaddr() + sa, _ := rsa.name.Sockaddr() return n, sa, nil } @@ -768,19 +779,18 @@ func (fd *FD) ReadFromInet4(buf []byte, sa4 *syscall.SockaddrInet4) (int, error) fd.pin('r', &buf[0]) - rsa := wsaRsaPool.Get().(*syscall.RawSockaddrAny) + rsa := newWSARsa() defer wsaRsaPool.Put(rsa) n, err := fd.execIO('r', func(o *operation) (qty uint32, err error) { - rsan := int32(unsafe.Sizeof(*rsa)) var flags uint32 - err = syscall.WSARecvFrom(fd.Sysfd, newWsaBuf(buf), 1, &qty, &flags, rsa, &rsan, &o.o, nil) + err = syscall.WSARecvFrom(fd.Sysfd, newWsaBuf(buf), 1, &qty, &flags, &rsa.name, &rsa.namelen, &o.o, nil) return qty, err }) err = fd.eofError(n, err) if err != nil { return n, err } - rawToSockaddrInet4(rsa, sa4) + rawToSockaddrInet4(&rsa.name, sa4) return n, err } @@ -799,19 +809,18 @@ func (fd *FD) ReadFromInet6(buf []byte, sa6 *syscall.SockaddrInet6) (int, error) fd.pin('r', &buf[0]) - rsa := wsaRsaPool.Get().(*syscall.RawSockaddrAny) + rsa := newWSARsa() defer wsaRsaPool.Put(rsa) n, err := fd.execIO('r', func(o *operation) (qty uint32, err error) { - rsan := int32(unsafe.Sizeof(*rsa)) var flags uint32 - err = syscall.WSARecvFrom(fd.Sysfd, newWsaBuf(buf), 1, &qty, &flags, rsa, &rsan, &o.o, nil) + err = syscall.WSARecvFrom(fd.Sysfd, newWsaBuf(buf), 1, &qty, &flags, &rsa.name, &rsa.namelen, &o.o, nil) return qty, err }) err = fd.eofError(n, err) if err != nil { return n, err } - rawToSockaddrInet6(rsa, sa6) + rawToSockaddrInet6(&rsa.name, sa6) return n, err } @@ -1371,7 +1380,9 @@ func (fd *FD) ReadMsg(p []byte, oob []byte, flags int) (int, int, int, syscall.S p = p[:maxRW] } - msg := newWSAMsg(p, oob, flags, true) + rsa := newWSARsa() + defer wsaRsaPool.Put(rsa) + msg := newWSAMsg(p, oob, flags, rsa) defer freeWSAMsg(msg) n, err := fd.execIO('r', func(o *operation) (qty uint32, err error) { err = windows.WSARecvMsg(fd.Sysfd, msg, &qty, &o.o, nil) @@ -1396,7 +1407,9 @@ func (fd *FD) ReadMsgInet4(p []byte, oob []byte, flags int, sa4 *syscall.Sockadd p = p[:maxRW] } - msg := newWSAMsg(p, oob, flags, true) + rsa := newWSARsa() + defer wsaRsaPool.Put(rsa) + msg := newWSAMsg(p, oob, flags, rsa) defer freeWSAMsg(msg) n, err := fd.execIO('r', func(o *operation) (qty uint32, err error) { err = windows.WSARecvMsg(fd.Sysfd, msg, &qty, &o.o, nil) @@ -1420,7 +1433,9 @@ func (fd *FD) ReadMsgInet6(p []byte, oob []byte, flags int, sa6 *syscall.Sockadd p = p[:maxRW] } - msg := newWSAMsg(p, oob, flags, true) + rsa := newWSARsa() + defer wsaRsaPool.Put(rsa) + msg := newWSAMsg(p, oob, flags, rsa) defer freeWSAMsg(msg) n, err := fd.execIO('r', func(o *operation) (qty uint32, err error) { err = windows.WSARecvMsg(fd.Sysfd, msg, &qty, &o.o, nil) @@ -1444,15 +1459,18 @@ func (fd *FD) WriteMsg(p []byte, oob []byte, sa syscall.Sockaddr) (int, int, err } defer fd.writeUnlock() - msg := newWSAMsg(p, oob, 0, sa != nil) - defer freeWSAMsg(msg) + var rsa *wsaRsa if sa != nil { + rsa = newWSARsa() + defer wsaRsaPool.Put(rsa) var err error - msg.Namelen, err = sockaddrToRaw(msg.Name, sa) + rsa.namelen, err = sockaddrToRaw(&rsa.name, sa) if err != nil { return 0, 0, err } } + msg := newWSAMsg(p, oob, 0, rsa) + defer freeWSAMsg(msg) n, err := fd.execIO('w', func(o *operation) (qty uint32, err error) { err = windows.WSASendMsg(fd.Sysfd, msg, 0, nil, &o.o, nil) return qty, err @@ -1471,11 +1489,14 @@ func (fd *FD) WriteMsgInet4(p []byte, oob []byte, sa *syscall.SockaddrInet4) (in } defer fd.writeUnlock() - msg := newWSAMsg(p, oob, 0, sa != nil) - defer freeWSAMsg(msg) + var rsa *wsaRsa if sa != nil { - msg.Namelen = sockaddrInet4ToRaw(msg.Name, sa) + rsa = newWSARsa() + defer wsaRsaPool.Put(rsa) + rsa.namelen = sockaddrInet4ToRaw(&rsa.name, sa) } + msg := newWSAMsg(p, oob, 0, rsa) + defer freeWSAMsg(msg) n, err := fd.execIO('w', func(o *operation) (qty uint32, err error) { err = windows.WSASendMsg(fd.Sysfd, msg, 0, nil, &o.o, nil) return qty, err @@ -1494,11 +1515,14 @@ func (fd *FD) WriteMsgInet6(p []byte, oob []byte, sa *syscall.SockaddrInet6) (in } defer fd.writeUnlock() - msg := newWSAMsg(p, oob, 0, sa != nil) - defer freeWSAMsg(msg) + var rsa *wsaRsa if sa != nil { - msg.Namelen = sockaddrInet6ToRaw(msg.Name, sa) + rsa = newWSARsa() + defer wsaRsaPool.Put(rsa) + rsa.namelen = sockaddrInet6ToRaw(&rsa.name, sa) } + msg := newWSAMsg(p, oob, 0, rsa) + defer freeWSAMsg(msg) n, err := fd.execIO('w', func(o *operation) (qty uint32, err error) { err = windows.WSASendMsg(fd.Sysfd, msg, 0, nil, &o.o, nil) return qty, err