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Commit 606afc7b authored by Paul Lawrence's avatar Paul Lawrence
Browse files

Fix deadlock caused by two-threaded property controls 

Two threaded property controls were introduced in ag/21063815 to prevent
DOS for power controls. However, this causes deadlocks, so limit the
second thread to just sys.powerctl messages.

Bug: 273785601
Test: Boots, power messages work
Ignore-AOSP-First: Security fix
Change-Id: Ie27dc3b0cd9e2d28e94f2ad398c55ee27bc35835
parent bfd626e7

init/property_service.cpp

+27 −23
Original line number Diff line number Diff line
@@ -117,7 +117,6 @@ static bool accept_messages = false; 
static std::mutex accept_messages_lock;

static std::thread property_service_thread;

static std::thread property_service_for_system_thread;

static std::mutex set_property_lock;



static std::unique_ptr<PersistWriteThread> persist_write_thread;
@@ -395,7 +394,11 @@ static std::optional<uint32_t> PropertySet(const std::string& name, const std::s 
        return {PROP_ERROR_INVALID_VALUE};

    }



    auto lock = std::lock_guard{set_property_lock};

    if (name == "sys.powerctl") {

        // No action here - NotifyPropertyChange will trigger the appropriate action, and since this

        // can come to the second thread, we mustn't call out to the __system_property_* functions

        // which support multiple readers but only one mutator.

    } else {

        prop_info* pi = (prop_info*)__system_property_find(name.c_str());

        if (pi != nullptr) {

            // ro.* properties are actually "write-once".
@@ -422,6 +425,7 @@ static std::optional<uint32_t> PropertySet(const std::string& name, const std::s 
            }

            WritePersistentProperty(name, value);

        }

    }



    NotifyPropertyChange(name, value);

    return {PROP_SUCCESS};