Guard against thread safety issues related to assertions

https://bugs.webkit.org/show_bug.cgi?id=268758
rdar://122321271

Reviewed by Chris Dumez.

Guard against thread safety issues related to assertions, since they are usually acquired on a non-main thread.

* Source/WebKit/UIProcess/Cocoa/ProcessAssertionCocoa.mm:
(WebKit::ProcessAssertion::acquireSync):
(WebKit::ProcessAssertion::~ProcessAssertion):
* Source/WebKit/UIProcess/ProcessAssertion.h:

Canonical link: https://commits.webkit.org/274122@main

Source/WebKit/UIProcess/Cocoa/ProcessAssertionCocoa.mm

@@ -358,6 +358,10 @@ static ASCIILiteral runningBoardDomainForAssertionType(ProcessAssertionType asse
     }
 }
 
+#if USE(EXTENSIONKIT)
+Lock ProcessAssertion::s_capabilityLock;
+#endif
+
 ProcessAssertion::ProcessAssertion(pid_t pid, const String& reason, ProcessAssertionType assertionType, const String& environmentIdentifier)
     : m_assertionType(assertionType)
     , m_pid(pid)
@@ -465,6 +469,7 @@ static ASCIILiteral runningBoardDomainForAssertionType(ProcessAssertionType asse
 {
     RELEASE_LOG(ProcessSuspension, "%p - ProcessAssertion::acquireSync Trying to take RBS assertion '%{public}s' for process with PID=%d", this, m_reason.utf8().data(), m_pid);
 #if USE(EXTENSIONKIT)
+    Locker locker { s_capabilityLock };
     if (m_process && m_capability) {
         NSError *error = nil;
         m_grant = [m_process grantCapability:m_capability->platformCapability().get() error:&error];
@@ -500,6 +505,7 @@ static ASCIILiteral runningBoardDomainForAssertionType(ProcessAssertionType asse
     }
 
 #if USE(EXTENSIONKIT)
+    Locker locker { s_capabilityLock };
     [m_grant invalidateWithError:nil];
 #endif
 }

Source/WebKit/UIProcess/ProcessAssertion.h

@@ -116,8 +116,9 @@ class ProcessAssertion : public ThreadSafeRefCountedAndCanMakeThreadSafeWeakPtr<
     Function<void()> m_prepareForInvalidationHandler;
     Function<void()> m_invalidationHandler;
 #if USE(EXTENSIONKIT)
+    static Lock s_capabilityLock;
     std::optional<AssertionCapability> m_capability;
-    RetainPtr<_SEGrant> m_grant;
+    RetainPtr<_SEGrant> m_grant WTF_GUARDED_BY_LOCK(s_capabilityLock);
     RetainPtr<_SEExtensionProcess> m_process;
 #endif
 };