Kernel: Lock socket mutex across {get,set}sockopt() and SO_ERROR updates

Since a socket can be accessed by multiple threads concurrently, we need
to protect shared data behind the socket mutex.

There's very likely more places where we need to fix this, the purpose
of this patch is to fix a VERIFY() failure in getsockopt() seen on CI.

Kernel/Net/IPv4Socket.cpp

@@ -505,6 +505,8 @@ ErrorOr<void> IPv4Socket::setsockopt(int level, int option, Userspace<const void
     if (level != IPPROTO_IP)
         return Socket::setsockopt(level, option, user_value, user_value_size);
 
+    MutexLocker locker(mutex());
+
     switch (option) {
     case IP_TTL: {
         if (user_value_size < sizeof(int))
@@ -569,6 +571,8 @@ ErrorOr<void> IPv4Socket::getsockopt(OpenFileDescription& description, int level
     if (level != IPPROTO_IP)
         return Socket::getsockopt(description, level, option, value, value_size);
 
+    MutexLocker locker(mutex());
+
     socklen_t size;
     TRY(copy_from_user(&size, value_size.unsafe_userspace_ptr()));
 

Kernel/Net/LocalSocket.cpp

@@ -386,6 +386,8 @@ ErrorOr<void> LocalSocket::getsockopt(OpenFileDescription& description, int leve
     if (level != SOL_SOCKET)
         return Socket::getsockopt(description, level, option, value, value_size);
 
+    MutexLocker locker(mutex());
+
     socklen_t size;
     TRY(copy_from_user(&size, value_size.unsafe_userspace_ptr()));
 

Kernel/Net/Socket.cpp

@@ -78,6 +78,8 @@ ErrorOr<void> Socket::queue_connection_from(NonnullRefPtr<Socket> peer)
 
 ErrorOr<void> Socket::setsockopt(int level, int option, Userspace<const void*> user_value, socklen_t user_value_size)
 {
+    MutexLocker locker(mutex());
+
     if (level != SOL_SOCKET)
         return ENOPROTOOPT;
     VERIFY(level == SOL_SOCKET);
@@ -133,6 +135,8 @@ ErrorOr<void> Socket::setsockopt(int level, int option, Userspace<const void*> u
 
 ErrorOr<void> Socket::getsockopt(OpenFileDescription&, int level, int option, Userspace<void*> value, Userspace<socklen_t*> value_size)
 {
+    MutexLocker locker(mutex());
+
     socklen_t size;
     TRY(copy_from_user(&size, value_size.unsafe_userspace_ptr()));
 

Kernel/Net/Socket.h

@@ -130,16 +130,22 @@ protected:
 
     Role m_role { Role::None };
 
-    ErrorOr<void> so_error() const { return m_so_error; }
+    ErrorOr<void> so_error() const
+    {
+        VERIFY(m_mutex.is_locked_by_current_thread());
+        return m_so_error;
+    }
 
     Error set_so_error(ErrnoCode error_code)
     {
+        MutexLocker locker(mutex());
         auto error = Error::from_errno(error_code);
         m_so_error = error;
         return error;
     }
     Error set_so_error(Error error)
     {
+        MutexLocker locker(mutex());
         m_so_error = error;
         return error;
     }