mirror of https://github.com/tailscale/tailscale/
ipn/ipnlocal: fix race in enterState
It would acquire the lock, calculate `nextState`, relase the lock, then call `enterState` which would acquire the lock again. There were obvious races there which could lead to nil panics as seen in a test in a different repo. ``` panic: runtime error: invalid memory address or nil pointer dereference [signal SIGSEGV: segmentation violation code=0x2 addr=0x70 pc=0x1050f2c7c] goroutine 42240 [running]: tailscale.com/ipn/ipnlocal.(*LocalBackend).enterStateLockedOnEntry(0x14002154e00, 0x6) tailscale.com/ipn/ipnlocal/local.go:3715 +0x30c tailscale.com/ipn/ipnlocal.(*LocalBackend).enterState(0x14002154e00?, 0x14002e3a140?) tailscale.com/ipn/ipnlocal/local.go:3663 +0x8c tailscale.com/ipn/ipnlocal.(*LocalBackend).stateMachine(0x14001f5e280?) tailscale.com/ipn/ipnlocal/local.go:3836 +0x2c tailscale.com/ipn/ipnlocal.(*LocalBackend).setWgengineStatus(0x14002154e00, 0x14002e3a190, {0x0?, 0x0?}) tailscale.com/ipn/ipnlocal/local.go:1193 +0x4d0 tailscale.com/wgengine.(*userspaceEngine).RequestStatus(0x14005d90300) tailscale.com/wgengine/userspace.go:1051 +0x80 tailscale.com/wgengine.NewUserspaceEngine.func2({0x14002e3a0a0, 0x2, 0x140025cce40?}) tailscale.com/wgengine/userspace.go:318 +0x1a0 tailscale.com/wgengine/magicsock.(*Conn).updateEndpoints(0x14002154700, {0x105c13eaf, 0xf}) tailscale.com/wgengine/magicsock/magicsock.go:531 +0x424 created by tailscale.com/wgengine/magicsock.(*Conn).ReSTUN in goroutine 42077 tailscale.com/wgengine/magicsock/magicsock.go:2142 +0x3a4 ``` Updates tailscale/corp#14480 Signed-off-by: Maisem Ali <maisem@tailscale.com>pull/9240/head
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