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tun: windows: set event before waiting 

In 097af6e ("tun: windows: protect reads from closing") we made sure no
functions are running when End() is called, to avoid a UaF. But we still
need to kick that event somehow, so that Read() is allowed to exit, in
order to release the lock. So this commit calls SetEvent, while moving
the closing boolean to be atomic so it can be modified without locks,
and then moves to a WaitGroup for the RCU-like pattern.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jason A. Donenfeld 2021-05-07 09:26:24 +02:00
parent db733ccd65
commit 69b39db0b4
1 changed files with 18 additions and 18 deletions
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36
tun/tun_windows.go
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@ -40,10 +40,10 @@ type NativeTun struct {
session wintun.Session
readWait windows.Handle
events chan Event
closing sync.RWMutex
running sync.WaitGroup
closeOnce sync.Once
close int32
forcedMTU int
close bool
}
var WintunPool, _ = wintun.MakePool("WireGuard")
@ -111,9 +111,9 @@ func CreateTUNWithRequestedGUID(ifname string, requestedGUID *windows.GUID, mtu
}
func (tun *NativeTun) Name() (string, error) {
tun.closing.RLock()
defer tun.closing.RUnlock()
if tun.close {
tun.running.Add(1)
defer tun.running.Done()
if atomic.LoadInt32(&tun.close) == 1 {
return "", os.ErrClosed
}
return tun.wt.Name()
@ -130,9 +130,9 @@ func (tun *NativeTun) Events() chan Event {
func (tun *NativeTun) Close() error {
var err error
tun.closeOnce.Do(func() {
tun.closing.Lock()
defer tun.closing.Unlock()
tun.close = true
atomic.StoreInt32(&tun.close, 1)
windows.SetEvent(tun.readWait)
tun.running.Wait()
tun.session.End()
if tun.wt != nil {
_, err = tun.wt.Delete(false)
@ -158,16 +158,16 @@ func (tun *NativeTun) ForceMTU(mtu int) {
// Note: Read() and Write() assume the caller comes only from a single thread; there's no locking.
func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
tun.closing.RLock()
defer tun.closing.RUnlock()
tun.running.Add(1)
defer tun.running.Done()
retry:
if tun.close {
if atomic.LoadInt32(&tun.close) == 1 {
return 0, os.ErrClosed
}
start := nanotime()
shouldSpin := atomic.LoadUint64(&tun.rate.current) >= spinloopRateThreshold && uint64(start-atomic.LoadInt64(&tun.rate.nextStartTime)) <= rateMeasurementGranularity*2
for {
if tun.close {
if atomic.LoadInt32(&tun.close) == 1 {
return 0, os.ErrClosed
}
packet, err := tun.session.ReceivePacket()
@ -199,9 +199,9 @@ func (tun *NativeTun) Flush() error {
}
func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
tun.closing.RLock()
defer tun.closing.RUnlock()
if tun.close {
tun.running.Add(1)
defer tun.running.Done()
if atomic.LoadInt32(&tun.close) == 1 {
return 0, os.ErrClosed
}
@ -225,9 +225,9 @@ func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
// LUID returns Windows interface instance ID.
func (tun *NativeTun) LUID() uint64 {
tun.closing.RLock()
defer tun.closing.RUnlock()
if tun.close {
tun.running.Add(1)
defer tun.running.Done()
if atomic.LoadInt32(&tun.close) == 1 {
return 0
}
return tun.wt.LUID()