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internal/poll: don't use stack-allocated WSAMsg parameters

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WSAMsg parameters should be passed to Windows as heap pointers instead
of stack pointers. This is because Windows might access the memory
after the syscall returned in case of a non-blocking operation (which
is the common case), and if the WSAMsg is on the stack, the Go
runtime might have moved it around.

Use a sync.Pool to cache WSAMsg structures to avoid a heap allocation
every time a WSAMsg is needed.

Fixes #74933

Cq-Include-Trybots: luci.golang.try:x_net-gotip-windows-amd64
Change-Id: I075e2ceb25cd545224ab3a10d404340faf19fc01
Reviewed-on: https://go-review.googlesource.com/c/go/+/698797
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This commit is contained in:
qmuntal 2025-08-25 09:57:49 +02:00 • committed by Quim Muntal
parent dae9e456ae
commit bfd130db02
1 changed files with 69 additions and 44 deletions
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101
src/internal/poll/fd_windows.go
View file

@ -144,19 +144,47 @@ func (o *operation) ClearBufs() {
o.bufs = o.bufs[:0] o.bufs = o.bufs[:0]
} }
func newWSAMsg(p []byte, oob []byte, flags int) windows.WSAMsg { // wsaMsgPool is a pool of WSAMsg structures that can only hold a single WSABuf.
return windows.WSAMsg{ var wsaMsgPool = sync.Pool{
Buffers: &syscall.WSABuf{ New: func() any {
Len: uint32(len(p)), return &windows.WSAMsg{
Buf: unsafe.SliceData(p), Buffers: &syscall.WSABuf{},
},
BufferCount: 1, BufferCount: 1,
Control: syscall.WSABuf{ }
},
}
// newWSAMsg creates a new WSAMsg with the provided parameters.
// Use [freeWSAMsg] to free it.
func newWSAMsg(p []byte, oob []byte, flags int, rsa *syscall.RawSockaddrAny) *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.
// TODO(qmuntal): investigate using runtime.Pinner keeping this path allocation-free.
// Use a pool to reuse allocations.
msg := wsaMsgPool.Get().(*windows.WSAMsg)
msg.Buffers.Len = uint32(len(p))
msg.Buffers.Buf = unsafe.SliceData(p)
msg.Control = syscall.WSABuf{
Len: uint32(len(oob)), Len: uint32(len(oob)),
Buf: unsafe.SliceData(oob), Buf: unsafe.SliceData(oob),
},
Flags: uint32(flags),
} }
msg.Flags = uint32(flags)
msg.Name = syscall.Pointer(unsafe.Pointer(rsa))
if rsa != nil {
msg.Namelen = int32(unsafe.Sizeof(*rsa))
} else {
msg.Namelen = 0
}
return msg
}
func freeWSAMsg(msg *windows.WSAMsg) {
// Clear pointers to buffers so they can be released by garbage collector.
msg.Buffers.Len = 0
msg.Buffers.Buf = nil
wsaMsgPool.Put(msg)
} }
// waitIO waits for the IO operation o to complete. // waitIO waits for the IO operation o to complete.
@ -1297,11 +1325,10 @@ func (fd *FD) ReadMsg(p []byte, oob []byte, flags int) (int, int, int, syscall.S
if o.rsa == nil { if o.rsa == nil {
o.rsa = new(syscall.RawSockaddrAny) o.rsa = new(syscall.RawSockaddrAny)
} }
msg := newWSAMsg(p, oob, flags) msg := newWSAMsg(p, oob, flags, o.rsa)
msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa)) defer freeWSAMsg(msg)
msg.Namelen = int32(unsafe.Sizeof(*o.rsa))
n, err := fd.execIO(o, func(o *operation) (qty uint32, err error) { n, err := fd.execIO(o, func(o *operation) (qty uint32, err error) {
err = windows.WSARecvMsg(fd.Sysfd, &msg, &qty, &o.o, nil) err = windows.WSARecvMsg(fd.Sysfd, msg, &qty, &o.o, nil)
return qty, err return qty, err
}) })
err = fd.eofError(n, err) err = fd.eofError(n, err)
@ -1327,11 +1354,10 @@ func (fd *FD) ReadMsgInet4(p []byte, oob []byte, flags int, sa4 *syscall.Sockadd
if o.rsa == nil { if o.rsa == nil {
o.rsa = new(syscall.RawSockaddrAny) o.rsa = new(syscall.RawSockaddrAny)
} }
msg := newWSAMsg(p, oob, flags) msg := newWSAMsg(p, oob, flags, o.rsa)
msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa)) defer freeWSAMsg(msg)
msg.Namelen = int32(unsafe.Sizeof(*o.rsa))
n, err := fd.execIO(o, func(o *operation) (qty uint32, err error) { n, err := fd.execIO(o, func(o *operation) (qty uint32, err error) {
err = windows.WSARecvMsg(fd.Sysfd, &msg, &qty, &o.o, nil) err = windows.WSARecvMsg(fd.Sysfd, msg, &qty, &o.o, nil)
return qty, err return qty, err
}) })
err = fd.eofError(n, err) err = fd.eofError(n, err)
@ -1356,11 +1382,10 @@ func (fd *FD) ReadMsgInet6(p []byte, oob []byte, flags int, sa6 *syscall.Sockadd
if o.rsa == nil { if o.rsa == nil {
o.rsa = new(syscall.RawSockaddrAny) o.rsa = new(syscall.RawSockaddrAny)
} }
msg := newWSAMsg(p, oob, flags) msg := newWSAMsg(p, oob, flags, o.rsa)
msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa)) defer freeWSAMsg(msg)
msg.Namelen = int32(unsafe.Sizeof(*o.rsa))
n, err := fd.execIO(o, func(o *operation) (qty uint32, err error) { n, err := fd.execIO(o, func(o *operation) (qty uint32, err error) {
err = windows.WSARecvMsg(fd.Sysfd, &msg, &qty, &o.o, nil) err = windows.WSARecvMsg(fd.Sysfd, msg, &qty, &o.o, nil)
return qty, err return qty, err
}) })
err = fd.eofError(n, err) err = fd.eofError(n, err)
@ -1382,20 +1407,20 @@ func (fd *FD) WriteMsg(p []byte, oob []byte, sa syscall.Sockaddr) (int, int, err
defer fd.writeUnlock() defer fd.writeUnlock()
o := &fd.wop o := &fd.wop
msg := newWSAMsg(p, oob, 0) if sa != nil && o.rsa == nil {
if sa != nil {
if o.rsa == nil {
o.rsa = new(syscall.RawSockaddrAny) o.rsa = new(syscall.RawSockaddrAny)
} }
len, err := sockaddrToRaw(o.rsa, sa) msg := newWSAMsg(p, oob, 0, o.rsa)
defer freeWSAMsg(msg)
if sa != nil {
var err error
msg.Namelen, err = sockaddrToRaw(o.rsa, sa)
if err != nil { if err != nil {
return 0, 0, err return 0, 0, err
} }
msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
msg.Namelen = len
} }
n, err := fd.execIO(o, func(o *operation) (qty uint32, err error) { n, err := fd.execIO(o, func(o *operation) (qty uint32, err error) {
err = windows.WSASendMsg(fd.Sysfd, &msg, 0, nil, &o.o, nil) err = windows.WSASendMsg(fd.Sysfd, msg, 0, nil, &o.o, nil)
return qty, err return qty, err
}) })
return n, int(msg.Control.Len), err return n, int(msg.Control.Len), err
@ -1413,16 +1438,16 @@ func (fd *FD) WriteMsgInet4(p []byte, oob []byte, sa *syscall.SockaddrInet4) (in
defer fd.writeUnlock() defer fd.writeUnlock()
o := &fd.wop o := &fd.wop
msg := newWSAMsg(p, oob, 0) if sa != nil && o.rsa == nil {
if sa != nil {
if o.rsa == nil {
o.rsa = new(syscall.RawSockaddrAny) o.rsa = new(syscall.RawSockaddrAny)
} }
msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa)) msg := newWSAMsg(p, oob, 0, o.rsa)
defer freeWSAMsg(msg)
if sa != nil {
msg.Namelen = sockaddrInet4ToRaw(o.rsa, sa) msg.Namelen = sockaddrInet4ToRaw(o.rsa, sa)
} }
n, err := fd.execIO(o, func(o *operation) (qty uint32, err error) { n, err := fd.execIO(o, func(o *operation) (qty uint32, err error) {
err = windows.WSASendMsg(fd.Sysfd, &msg, 0, nil, &o.o, nil) err = windows.WSASendMsg(fd.Sysfd, msg, 0, nil, &o.o, nil)
return qty, err return qty, err
}) })
return n, int(msg.Control.Len), err return n, int(msg.Control.Len), err
@ -1440,16 +1465,16 @@ func (fd *FD) WriteMsgInet6(p []byte, oob []byte, sa *syscall.SockaddrInet6) (in
defer fd.writeUnlock() defer fd.writeUnlock()
o := &fd.wop o := &fd.wop
msg := newWSAMsg(p, oob, 0) if sa != nil && o.rsa == nil {
if sa != nil {
if o.rsa == nil {
o.rsa = new(syscall.RawSockaddrAny) o.rsa = new(syscall.RawSockaddrAny)
} }
msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa)) msg := newWSAMsg(p, oob, 0, o.rsa)
defer freeWSAMsg(msg)
if sa != nil {
msg.Namelen = sockaddrInet6ToRaw(o.rsa, sa) msg.Namelen = sockaddrInet6ToRaw(o.rsa, sa)
} }
n, err := fd.execIO(o, func(o *operation) (qty uint32, err error) { n, err := fd.execIO(o, func(o *operation) (qty uint32, err error) {
err = windows.WSASendMsg(fd.Sysfd, &msg, 0, nil, &o.o, nil) err = windows.WSASendMsg(fd.Sysfd, msg, 0, nil, &o.o, nil)
return qty, err return qty, err
}) })
return n, int(msg.Control.Len), err return n, int(msg.Control.Len), err