Fix cancellation race problem for aysnc DNS API
This problem might cause double-close fd and result in app crash
or unexpected behaviour
Bug: 129317069
Test: atest DnsResolverTest
manual test with delaying response callback/cancel
Change-Id: I223234f527edafc51d34fa6be390419c05def8d8
diff --git a/core/java/android/net/DnsResolver.java b/core/java/android/net/DnsResolver.java
index 5980251..f9e0af2 100644
--- a/core/java/android/net/DnsResolver.java
+++ b/core/java/android/net/DnsResolver.java
@@ -205,6 +205,7 @@
if (cancellationSignal != null && cancellationSignal.isCanceled()) {
return;
}
+ final Object lock = new Object();
final FileDescriptor queryfd;
try {
queryfd = resNetworkSend((network != null
@@ -214,8 +215,8 @@
return;
}
- maybeAddCancellationSignal(cancellationSignal, queryfd);
- registerFDListener(executor, queryfd, callback);
+ maybeAddCancellationSignal(cancellationSignal, queryfd, lock);
+ registerFDListener(executor, queryfd, callback, cancellationSignal, lock);
}
/**
@@ -242,6 +243,7 @@
if (cancellationSignal != null && cancellationSignal.isCanceled()) {
return;
}
+ final Object lock = new Object();
final FileDescriptor queryfd;
try {
queryfd = resNetworkQuery((network != null
@@ -251,31 +253,37 @@
return;
}
- maybeAddCancellationSignal(cancellationSignal, queryfd);
- registerFDListener(executor, queryfd, callback);
+ maybeAddCancellationSignal(cancellationSignal, queryfd, lock);
+ registerFDListener(executor, queryfd, callback, cancellationSignal, lock);
}
private <T> void registerFDListener(@NonNull Executor executor,
- @NonNull FileDescriptor queryfd, @NonNull AnswerCallback<T> answerCallback) {
+ @NonNull FileDescriptor queryfd, @NonNull AnswerCallback<T> answerCallback,
+ @Nullable CancellationSignal cancellationSignal, @NonNull Object lock) {
Looper.getMainLooper().getQueue().addOnFileDescriptorEventListener(
queryfd,
FD_EVENTS,
(fd, events) -> {
executor.execute(() -> {
- byte[] answerbuf = null;
- try {
- answerbuf = resNetworkResult(fd);
- } catch (ErrnoException e) {
- Log.e(TAG, "resNetworkResult:" + e.toString());
- answerCallback.onQueryException(e);
- return;
- }
+ synchronized (lock) {
+ if (cancellationSignal != null && cancellationSignal.isCanceled()) {
+ return;
+ }
+ byte[] answerbuf = null;
+ try {
+ answerbuf = resNetworkResult(fd);
+ } catch (ErrnoException e) {
+ Log.e(TAG, "resNetworkResult:" + e.toString());
+ answerCallback.onQueryException(e);
+ return;
+ }
- try {
- answerCallback.onAnswer(
- answerCallback.parser.parse(answerbuf));
- } catch (ParseException e) {
- answerCallback.onParseException(e);
+ try {
+ answerCallback.onAnswer(
+ answerCallback.parser.parse(answerbuf));
+ } catch (ParseException e) {
+ answerCallback.onParseException(e);
+ }
}
});
// Unregister this fd listener
@@ -284,14 +292,16 @@
}
private void maybeAddCancellationSignal(@Nullable CancellationSignal cancellationSignal,
- @NonNull FileDescriptor queryfd) {
+ @NonNull FileDescriptor queryfd, @NonNull Object lock) {
if (cancellationSignal == null) return;
- cancellationSignal.setOnCancelListener(
- () -> {
- Looper.getMainLooper().getQueue()
- .removeOnFileDescriptorEventListener(queryfd);
- resNetworkCancel(queryfd);
- });
+ cancellationSignal.setOnCancelListener(() -> {
+ synchronized (lock) {
+ if (!queryfd.valid()) return;
+ Looper.getMainLooper().getQueue()
+ .removeOnFileDescriptorEventListener(queryfd);
+ resNetworkCancel(queryfd);
+ }
+ });
}
private static class DnsAddressAnswer extends DnsPacket {