[LOG4J2-3452] Race condition in FileUtils.mkdir()

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.13.0
• Assignee: Unassigned
• Reporter: Stefan Vodita
• Created: 29/Mar/22 12:39
• Updated: 08/Dec/23 18:56
• Resolved: 30/Mar/22 21:16

Description

I noticed an error like:

ERROR Unable to create file ...

at org.apache.logging.log4j.core.util.FileUtils.mkdir(FileUtils.java:118)

 

The error could be due to a race condition:

Thread A: dir.exists() -> false

Thread B: dir.exists() -> false

Thread B: dir.mkdirs() -> succeeds

Thread A: dir.mkdirs() -> throws exception

 

I wrote a unit test which reproduces the error:

public void testMkdirConcurrent() throws IOException {
        final File file = new File("target/test/test");

        for (int i = 0; i < 1000; i++) {
            new Thread(() -> assertDoesNotThrow(() -> FileUtils.mkdir(file, true))).start();

        org.apache.commons.io.FileUtils.deleteDirectory(file);
}

 

As a fix, we can use Files.createDirectories(), since this does the existence check and creation as one atomic operation.

 

I will create a PR with the unit test and a fix.

 

 

Issue Links

• links to: GitHub Pull Request #809