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joepembevy
joepembe
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Fix NPE in ThrowableStackTraceRenderer due to concurrent mutation of suppressed exceptions (#3934)
Co-authored-by: Volkan Yazıcı <[email protected]>
1 parent 84c7716 commit 7125d93

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+105
-12
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4 files changed

+105
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‎log4j-core-test/src/test/java/org/apache/logging/log4j/core/pattern/ThrowablePatternConverterTest.java‎

Lines changed: 67 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -26,14 +26,21 @@
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import java.nio.charset.Charset;
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import java.nio.charset.StandardCharsets;
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import java.util.List;
29+
import java.util.concurrent.CountDownLatch;
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import java.util.concurrent.ExecutorService;
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import java.util.concurrent.Executors;
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import java.util.concurrent.atomic.AtomicInteger;
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import java.util.concurrent.locks.LockSupport;
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import java.util.stream.Collectors;
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import java.util.stream.IntStream;
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import java.util.stream.Stream;
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import org.apache.logging.log4j.Level;
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import org.apache.logging.log4j.core.LogEvent;
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import org.apache.logging.log4j.core.impl.Log4jLogEvent;
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import org.apache.logging.log4j.core.layout.PatternLayout;
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import org.jspecify.annotations.Nullable;
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import org.junit.jupiter.api.Nested;
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import org.junit.jupiter.api.RepeatedTest;
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import org.junit.jupiter.api.Test;
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import org.junit.jupiter.params.ParameterizedTest;
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import org.junit.jupiter.params.provider.MethodSource;
@@ -435,6 +442,66 @@ private static String normalizeStackTrace(final String stackTrace, final String
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// We replace the `~[?:1.8.0_422]` suffix of such classes with `~[?:0]`.
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.replaceAll(" ~\\[\\?:[^]]+](\\Q" + conversionEnding + "\\E|$)", " ~[?:0]$1");
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}
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@RepeatedTest(10)
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@Issue("https://github.com/apache/logging-log4j2/issues/3929")
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void concurrent_suppressed_mutation_should_not_cause_failure() throws Exception {
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// Test constants
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final int threadCount = Math.max(8, Runtime.getRuntime().availableProcessors());
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final ExecutorService executor = Executors.newFixedThreadPool(threadCount);
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final Exception exception = new Exception();
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final CountDownLatch startLatch =
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new CountDownLatch(threadCount + /* the main thread invoking the rendering: */ 1);
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final int exceptionPerThreadCount = 100;
457+
final AtomicInteger runningThreadCountRef = new AtomicInteger(threadCount);
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// Schedule threads that will start adding suppressed exceptions with the start signal
460+
for (int threadIndex = 0; threadIndex < threadCount; threadIndex++) {
461+
final int threadIndex_ = threadIndex;
462+
executor.submit(() -> {
463+
try {
464+
List<Exception> exceptions = IntStream.range(0, exceptionPerThreadCount)
465+
.mapToObj(exceptionIndex -> new Exception(threadIndex_ + "-" + exceptionIndex))
466+
.collect(Collectors.toList());
467+
startLatch.countDown();
468+
startLatch.await();
469+
for (int exceptionIndex = 0; exceptionIndex < exceptionPerThreadCount; exceptionIndex++) {
470+
exception.addSuppressed(exceptions.get(exceptionIndex));
471+
// Give some time slack to increase randomness
472+
LockSupport.parkNanos(1);
473+
}
474+
} catch (InterruptedException ignored) {
475+
// Restore the interrupt
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Thread.currentThread().interrupt();
477+
} finally {
478+
runningThreadCountRef.decrementAndGet();
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}
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});
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}
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// Create the formatter
484+
final List<PatternFormatter> patternFormatters = PATTERN_PARSER.parse(patternPrefix, false, true, true);
485+
assertThat(patternFormatters).hasSize(1);
486+
final PatternFormatter patternFormatter = patternFormatters.get(0);
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// Create the log event and the layout buffer
489+
final LogEvent logEvent = Log4jLogEvent.newBuilder()
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.setThrown(exception)
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.setLevel(LEVEL)
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.build();
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final StringBuilder buffer = new StringBuilder(16384);
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// Trigger the start latch and format the exception
496+
startLatch.countDown();
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startLatch.await();
498+
while (runningThreadCountRef.get() > 0) {
499+
// Give some time slack to increase randomness
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LockSupport.parkNanos(1);
501+
patternFormatter.format(logEvent, buffer);
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buffer.setLength(0);
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}
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}
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}
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static String convert(final String pattern) {

‎log4j-core/src/main/java/org/apache/logging/log4j/core/pattern/ThrowableInvertedStackTraceRenderer.java‎

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -60,6 +60,7 @@ private void renderThrowable(
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buffer.append(']');
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buffer.append(lineSeparator);
6262
} else {
63+
final Context.Metadata metadata = context.metadataByThrowable.get(throwable);
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lineCapacityAcquired = renderCause(
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buffer,
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throwable.getCause(),
@@ -73,9 +74,8 @@ private void renderThrowable(
7374
}
7475
renderThrowableMessage(buffer, throwable);
7576
buffer.append(lineSeparator);
76-
renderStackTraceElements(buffer, throwable, context, prefix, lineSeparator);
77-
renderSuppressed(
78-
buffer, throwable.getSuppressed(), context, visitedThrowables, prefix + '\t', lineSeparator);
77+
renderStackTraceElements(buffer, throwable, context, metadata, prefix, lineSeparator);
78+
renderSuppressed(buffer, metadata.suppressed, context, visitedThrowables, prefix + '\t', lineSeparator);
7979
}
8080
}
8181

‎log4j-core/src/main/java/org/apache/logging/log4j/core/pattern/ThrowableStackTraceRenderer.java‎

Lines changed: 22 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -95,11 +95,11 @@ private void renderThrowable(
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buffer.append(']');
9696
buffer.append(lineSeparator);
9797
} else {
98+
final Context.Metadata metadata = context.metadataByThrowable.get(throwable);
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renderThrowableMessage(buffer, throwable);
99100
buffer.append(lineSeparator);
100-
renderStackTraceElements(buffer, throwable, context, prefix, lineSeparator);
101-
renderSuppressed(
102-
buffer, throwable.getSuppressed(), context, visitedThrowables, prefix + '\t', lineSeparator);
101+
renderStackTraceElements(buffer, throwable, context, metadata, prefix, lineSeparator);
102+
renderSuppressed(buffer, metadata.suppressed, context, visitedThrowables, prefix + '\t', lineSeparator);
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renderCause(buffer, throwable.getCause(), context, visitedThrowables, prefix, lineSeparator);
104104
}
105105
}
@@ -150,10 +150,10 @@ final void renderStackTraceElements(
150150
final StringBuilder buffer,
151151
final Throwable throwable,
152152
final C context,
153+
final Context.Metadata metadata,
153154
final String prefix,
154155
final String lineSeparator) {
155156
context.ignoredStackTraceElementCount = 0;
156-
final Context.Metadata metadata = context.metadataByThrowable.get(throwable);
157157
final StackTraceElement[] stackTraceElements = throwable.getStackTrace();
158158
for (int i = 0; i < metadata.stackLength; i++) {
159159
renderStackTraceElement(buffer, stackTraceElements[i], context, prefix, lineSeparator);
@@ -268,9 +268,19 @@ static final class Metadata {
268268
*/
269269
final int stackLength;
270270

271-
private Metadata(final int commonElementCount, final int stackLength) {
271+
/**
272+
* The suppressed exceptions attached to this {@link Throwable}.
273+
* This needs to be captured separately since {@link Throwable#getSuppressed()} can change.
274+
*
275+
* @see <a href="https://github.com/apache/logging-log4j2/issues/3929">#3929</a>
276+
* @see <a href="https://github.com/apache/logging-log4j2/pull/3934">#3934</a>
277+
*/
278+
final Throwable[] suppressed;
279+
280+
private Metadata(final int commonElementCount, final int stackLength, final Throwable[] suppressed) {
272281
this.commonElementCount = commonElementCount;
273282
this.stackLength = stackLength;
283+
this.suppressed = suppressed;
274284
}
275285

276286
static Map<Throwable, Metadata> ofThrowable(final Throwable throwable) {
@@ -288,11 +298,12 @@ private static void populateMetadata(
288298
// Populate metadata of the current throwable
289299
@Nullable
290300
final StackTraceElement[] rootTrace = parentThrowable == null ? null : parentThrowable.getStackTrace();
291-
final Metadata metadata = populateMetadata(rootTrace, throwable.getStackTrace());
301+
final Metadata metadata =
302+
populateMetadata(rootTrace, throwable.getStackTrace(), throwable.getSuppressed());
292303
metadataByThrowable.put(throwable, metadata);
293304

294305
// Populate metadata of suppressed exceptions
295-
for (final Throwable suppressed : throwable.getSuppressed()) {
306+
for (final Throwable suppressed : metadata.suppressed) {
296307
if (!visitedThrowables.contains(suppressed)) {
297308
visitedThrowables.add(suppressed);
298309
populateMetadata(metadataByThrowable, visitedThrowables, throwable, suppressed);
@@ -308,7 +319,9 @@ private static void populateMetadata(
308319
}
309320

310321
private static Metadata populateMetadata(
311-
@Nullable final StackTraceElement[] parentTrace, final StackTraceElement[] currentTrace) {
322+
@Nullable final StackTraceElement[] parentTrace,
323+
final StackTraceElement[] currentTrace,
324+
final Throwable[] suppressed) {
312325
int commonElementCount;
313326
int stackLength;
314327
if (parentTrace != null) {
@@ -326,7 +339,7 @@ private static Metadata populateMetadata(
326339
commonElementCount = 0;
327340
stackLength = currentTrace.length;
328341
}
329-
return new Metadata(commonElementCount, stackLength);
342+
return new Metadata(commonElementCount, stackLength, suppressed);
330343
}
331344
}
332345
}

‎src/changelog/2.25.1/3929_ThrowableStackTraceRenderer-npe.xml‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,13 @@
1+
<?xml version="1.0" encoding="UTF-8"?>
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<entry xmlns="https://logging.apache.org/xml/ns"
3+
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="
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https://logging.apache.org/xml/ns
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https://logging.apache.org/xml/ns/log4j-changelog-0.xsd"
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type="fixed">
8+
<issue id="3929" link="https://github.com/apache/logging-log4j2/issues/3929"/>
9+
<issue id="3934" link="https://github.com/apache/logging-log4j2/pull/3934"/>
10+
<description format="asciidoc">
11+
Fixes `NullPointerException` thrown by `ThrowableStackTraceRenderer` when suppressed exceptions are mutated concurrently.
12+
</description>
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</entry>

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