From 12269c2761734b15625017d8565745096325392f Mon Sep 17 00:00:00 2001 From: Martin Basovnik Date: Fri, 10 Nov 2023 11:10:12 +0100 Subject: [PATCH] device: fix possible deadlock in close method There is a possible deadlock in `device.Close()` when you try to close the device very soon after its start. The problem is that two different methods acquire the same locks in different order: 1. device.Close() - device.ipcMutex.Lock() - device.state.Lock() 2. device.changeState(deviceState) - device.state.Lock() - device.ipcMutex.Lock() Reproducer: func TestDevice_deadlock(t *testing.T) { d := randDevice(t) d.Close() } Problem: $ go clean -testcache && go test -race -timeout 3s -run TestDevice_deadlock ./device | grep -A 10 sync.runtime_SemacquireMutex sync.runtime_SemacquireMutex(0xc000117d20?, 0x94?, 0x0?) /usr/local/opt/go/libexec/src/runtime/sema.go:77 +0x25 sync.(*Mutex).lockSlow(0xc000130518) /usr/local/opt/go/libexec/src/sync/mutex.go:171 +0x213 sync.(*Mutex).Lock(0xc000130518) /usr/local/opt/go/libexec/src/sync/mutex.go:90 +0x55 golang.zx2c4.com/wireguard/device.(*Device).Close(0xc000130500) /Users/martin.basovnik/git/basovnik/wireguard-go/device/device.go:373 +0xb6 golang.zx2c4.com/wireguard/device.TestDevice_deadlock(0x0?) /Users/martin.basovnik/git/basovnik/wireguard-go/device/device_test.go:480 +0x2c testing.tRunner(0xc00014c000, 0x131d7b0) -- sync.runtime_SemacquireMutex(0xc000130564?, 0x60?, 0xc000130548?) /usr/local/opt/go/libexec/src/runtime/sema.go:77 +0x25 sync.(*Mutex).lockSlow(0xc000130750) /usr/local/opt/go/libexec/src/sync/mutex.go:171 +0x213 sync.(*Mutex).Lock(0xc000130750) /usr/local/opt/go/libexec/src/sync/mutex.go:90 +0x55 sync.(*RWMutex).Lock(0xc000130750) /usr/local/opt/go/libexec/src/sync/rwmutex.go:147 +0x45 golang.zx2c4.com/wireguard/device.(*Device).upLocked(0xc000130500) /Users/martin.basovnik/git/basovnik/wireguard-go/device/device.go:179 +0x72 golang.zx2c4.com/wireguard/device.(*Device).changeState(0xc000130500, 0x1) Signed-off-by: Martin Basovnik Signed-off-by: Jason A. Donenfeld --- device/device.go | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/device/device.go b/device/device.go index ca26d00..83c33ee 100644 --- a/device/device.go +++ b/device/device.go @@ -368,10 +368,10 @@ func (device *Device) RemoveAllPeers() { } func (device *Device) Close() { - device.ipcMutex.Lock() - defer device.ipcMutex.Unlock() device.state.Lock() defer device.state.Unlock() + device.ipcMutex.Lock() + defer device.ipcMutex.Unlock() if device.isClosed() { return }