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Make PendingWriteQueue.recycle() update its state before triggering an event

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Related: #3212

Motivation:

PendingWriteQueue.recycle() updates its data structure after triggering
a channelWritabilityChanged() event. It causes a rare corruption such as
double free when channelWritabilityChanged() method accesses the
PendingWriteQueue.

Modifications:

Update the state of PendingWriteQueue before triggering an event.

Result:

Fix a rare double-free problem
This commit is contained in:
Trustin Lee 2014-12-07 23:24:19 +09:00
parent 1122189771
commit 1e35d06efb
2 changed files with 80 additions and 24 deletions
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9
transport/src/main/java/io/netty/channel/PendingWriteQueue.java
View File

@ -217,11 +217,11 @@ public final class PendingWriteQueue {
}
private void recycle(PendingWrite write) {
PendingWrite next = write.next;
final PendingWrite next = write.next;
final long writeSize = write.size;
buffer.decrementPendingOutboundBytes(write.size);
write.recycle();
size --;
if (next == null) {
// Handled last PendingWrite so rest head and tail
head = tail = null;
@ -230,6 +230,9 @@ public final class PendingWriteQueue {
head = next;
assert size > 0;
}
write.recycle();
buffer.decrementPendingOutboundBytes(writeSize);
}
private static void safeFail(ChannelPromise promise, Throwable cause) {

95
transport/src/test/java/io/netty/channel/PendingWriteQueueTest.java
View File

@ -20,9 +20,13 @@ import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.embedded.EmbeddedChannel;
import io.netty.util.CharsetUtil;
import org.junit.Assert;
import org.junit.Test;
import java.util.concurrent.atomic.AtomicReference;
import static org.hamcrest.Matchers.*;
import static org.junit.Assert.*;
public class PendingWriteQueueTest {
@Test
@ -30,7 +34,7 @@ public class PendingWriteQueueTest {
assertWrite(new TestHandler() {
@Override
public void flush(ChannelHandlerContext ctx) throws Exception {
Assert.assertFalse("Should not be writable anymore", ctx.channel().isWritable());
assertFalse("Should not be writable anymore", ctx.channel().isWritable());
ChannelFuture future = queue.removeAndWrite();
future.addListener(new ChannelFutureListener() {
@ -49,7 +53,7 @@ public class PendingWriteQueueTest {
assertWrite(new TestHandler() {
@Override
public void flush(ChannelHandlerContext ctx) throws Exception {
Assert.assertFalse("Should not be writable anymore", ctx.channel().isWritable());
assertFalse("Should not be writable anymore", ctx.channel().isWritable());
ChannelFuture future = queue.removeAndWriteAll();
future.addListener(new ChannelFutureListener() {
@ -86,6 +90,55 @@ public class PendingWriteQueueTest {
}, 3);
}
@Test
public void shouldFireChannelWritabilityChangedAfterRemoval() {
final AtomicReference<ChannelHandlerContext> ctxRef = new AtomicReference<ChannelHandlerContext>();
final AtomicReference<PendingWriteQueue> queueRef = new AtomicReference<PendingWriteQueue>();
final ByteBuf msg = Unpooled.copiedBuffer("test", CharsetUtil.US_ASCII);
final EmbeddedChannel channel = new EmbeddedChannel(new ChannelInboundHandlerAdapter() {
@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
ctxRef.set(ctx);
queueRef.set(new PendingWriteQueue(ctx));
}
@Override
public void channelWritabilityChanged(ChannelHandlerContext ctx) throws Exception {
final PendingWriteQueue queue = queueRef.get();
final ByteBuf msg = (ByteBuf) queue.current();
if (msg == null) {
return;
}
assertThat(msg.refCnt(), is(1));
// This call will trigger another channelWritabilityChanged() event because the number of
// pending bytes will go below the low watermark.
//
// If PendingWriteQueue.remove() did not remove the current entry before triggering
// channelWritabilityChanged() event, we will end up with attempting to remove the same
// element twice, resulting in the double release.
queue.remove();
assertThat(msg.refCnt(), is(0));
}
});
channel.config().setWriteBufferLowWaterMark(1);
channel.config().setWriteBufferHighWaterMark(3);
final PendingWriteQueue queue = queueRef.get();
// Trigger channelWritabilityChanged() by adding a message that's larger than the high watermark.
queue.add(msg, channel.newPromise());
channel.finish();
assertThat(msg.refCnt(), is(0));
}
private static void assertWrite(ChannelHandler handler, int count) {
final ByteBuf buffer = Unpooled.copiedBuffer("Test", CharsetUtil.US_ASCII);
final EmbeddedChannel channel = new EmbeddedChannel(handler);
@ -96,29 +149,29 @@ public class PendingWriteQueueTest {
for (int i = 0; i < buffers.length; i++) {
buffers[i] = buffer.duplicate().retain();
}
Assert.assertTrue(channel.writeOutbound(buffers));
Assert.assertTrue(channel.finish());
assertTrue(channel.writeOutbound(buffers));
assertTrue(channel.finish());
channel.closeFuture().syncUninterruptibly();
for (int i = 0; i < buffers.length; i++) {
assertBuffer(channel, buffer);
}
buffer.release();
Assert.assertNull(channel.readOutbound());
assertNull(channel.readOutbound());
}
private static void assertBuffer(EmbeddedChannel channel, ByteBuf buffer) {
ByteBuf written = (ByteBuf) channel.readOutbound();
Assert.assertEquals(buffer, written);
assertEquals(buffer, written);
written.release();
}
private static void assertQueueEmpty(PendingWriteQueue queue) {
Assert.assertTrue(queue.isEmpty());
Assert.assertEquals(0, queue.size());
Assert.assertNull(queue.current());
Assert.assertNull(queue.removeAndWrite());
Assert.assertNull(queue.removeAndWriteAll());
assertTrue(queue.isEmpty());
assertEquals(0, queue.size());
assertNull(queue.current());
assertNull(queue.removeAndWrite());
assertNull(queue.removeAndWriteAll());
}
private static void assertWriteFails(ChannelHandler handler, int count) {
@ -129,16 +182,16 @@ public class PendingWriteQueueTest {
buffers[i] = buffer.duplicate().retain();
}
try {
Assert.assertFalse(channel.writeOutbound(buffers));
Assert.fail();
assertFalse(channel.writeOutbound(buffers));
fail();
} catch (Exception e) {
Assert.assertTrue(e instanceof TestException);
assertTrue(e instanceof TestException);
}
Assert.assertFalse(channel.finish());
assertFalse(channel.finish());
channel.closeFuture().syncUninterruptibly();
buffer.release();
Assert.assertNull(channel.readOutbound());
assertNull(channel.readOutbound());
}
private static class TestHandler extends ChannelDuplexHandler {
@ -149,15 +202,15 @@ public class PendingWriteQueueTest {
public void channelActive(ChannelHandlerContext ctx) throws Exception {
super.channelActive(ctx);
assertQueueEmpty(queue);
Assert.assertTrue("Should be writable", ctx.channel().isWritable());
assertTrue("Should be writable", ctx.channel().isWritable());
}
@Override
public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
queue.add(msg, promise);
Assert.assertFalse(queue.isEmpty());
Assert.assertEquals(++ expectedSize, queue.size());
Assert.assertNotNull(queue.current());
assertFalse(queue.isEmpty());
assertEquals(++expectedSize, queue.size());
assertNotNull(queue.current());
}
@Override