mac/common: fix usage of vo struct after vo uninit race

we keep track of the current vo struct to flag for events that are
initiated async by various thread from different system notifications.
the problem here is the usage of that vo struct after uninit.

make accessing of that vo struct atomic and clear it on uninit, so it
can't be used afterwards by concurrent threads from system
notifications or events.

Fixes #15088

video/out/cocoa_cb_common.swift

@@ -40,7 +40,7 @@ class CocoaCB: Common, EventSubscriber {
     }
 
     func preinit(_ vo: UnsafeMutablePointer<vo>) {
-        self.vo = vo
+        eventsLock.withLock { self.vo = vo }
         input = InputHelper(vo.pointee.input_ctx, option)
 
         if backendState == .uninitialized {
@@ -57,12 +57,13 @@ class CocoaCB: Common, EventSubscriber {
     }
 
     func uninit() {
+        eventsLock.withLock { self.vo = nil }
         window?.orderOut(nil)
         window?.close()
     }
 
     func reconfig(_ vo: UnsafeMutablePointer<vo>) {
-        self.vo = vo
+        eventsLock.withLock { self.vo = vo }
         if backendState == .needsInit {
             DispatchQueue.main.sync { self.initBackend(vo) }
         } else if option.vo.auto_window_resize {

video/out/mac/common.swift

@@ -22,7 +22,6 @@ class Common: NSObject {
     var option: OptionHelper
     var input: InputHelper?
     var log: LogHelper
-    var vo: UnsafeMutablePointer<vo>?
     let queue: DispatchQueue = DispatchQueue(label: "io.mpv.queue")
 
     @objc var window: Window?
@@ -32,6 +31,7 @@ class Common: NSObject {
     var link: CVDisplayLink?
 
     let eventsLock = NSLock()
+    var vo: UnsafeMutablePointer<vo>?
     var events: Int = 0
 
     var lightSensor: io_connect_t = 0
@@ -145,6 +145,7 @@ class Common: NSObject {
     }
 
     func uninitCommon() {
+        eventsLock.withLock { self.vo = nil }
         setCursorVisibility(true)
         stopDisplaylink()
         uninitLightSensor()
@@ -455,24 +456,20 @@ class Common: NSObject {
     }
 
     func flagEvents(_ ev: Int) {
-        eventsLock.lock()
+        eventsLock.withLock {
             events |= ev
-        eventsLock.unlock()
-
-        guard let vo = vo else {
-            log.warning("vo nil in flagEvents")
-            return
-        }
+            guard let vo = vo else { return }
             vo_wakeup(vo)
         }
+    }
 
     func checkEvents() -> Int {
-        eventsLock.lock()
+        eventsLock.withLock {
             let ev = events
             events = 0
-        eventsLock.unlock()
             return ev
         }
+    }
 
     func windowDidEndAnimation() {}
     func windowSetToFullScreen() {}

video/out/mac_common.swift

@@ -29,7 +29,7 @@ class MacCommon: Common {
         let log = LogHelper(mp_log_new(vo, vo.pointee.log, "mac"))
         let option = OptionHelper(vo, vo.pointee.global)
         super.init(option, log)
-        self.vo = vo
+        eventsLock.withLock { self.vo = vo }
         input = InputHelper(vo.pointee.input_ctx, option)
         presentation = Presentation(common: self)
         timer = PreciseTimer(common: self)
@@ -41,7 +41,7 @@ class MacCommon: Common {
     }
 
     @objc func config(_ vo: UnsafeMutablePointer<vo>) -> Bool {
-        self.vo = vo
+        eventsLock.withLock { self.vo = vo }
 
         DispatchQueue.main.sync {
             let previousActiveApp = getActiveApp()