Merge pull request #13746 from nextcloud/backport/13739/stable13

[stable13] cleanup shared lock if changing to exclusive lock failed

lib/private/Files/View.php

@@ -1139,7 +1139,13 @@ private function basicOperation($operation, $path, $hooks = [], $extraParam = nu
 			list($storage, $internalPath) = Filesystem::resolvePath($absolutePath . $postFix);
 			if ($run and $storage) {
 				if (in_array('write', $hooks) || in_array('delete', $hooks)) {
-					$this->changeLock($path, ILockingProvider::LOCK_EXCLUSIVE);
+					try {
+						$this->changeLock($path, ILockingProvider::LOCK_EXCLUSIVE);
+					} catch (LockedException $e) {
+						// release the shared lock we acquired before quiting
+						$this->unlockFile($path, ILockingProvider::LOCK_SHARED);
+						throw $e;
+					}
 				}
 				try {
 					if (!is_null($extraParam)) {

tests/lib/Files/ViewTest.php

@@ -1987,6 +1987,37 @@ function () {
 		$this->assertNull($this->getFileLockType($view, $path), 'File got unlocked after exception');
 	}
 
+	public function testLockBasicOperationUnlocksAfterLockException() {
+		$view = new View('/' . $this->user . '/files/');
+
+		$storage = new Temporary([]);
+
+		Filesystem::mount($storage, array(), $this->user . '/');
+
+		$storage->mkdir('files');
+		$storage->mkdir('files/dir');
+		$storage->file_put_contents('files/test.txt', 'blah');
+		$storage->getScanner()->scan('files');
+
+		// get a shared lock
+		$handle = $view->fopen('test.txt', 'r');
+
+		$thrown = false;
+		try {
+			// try (and fail) to get a write lock
+			$view->unlink('test.txt');
+		} catch (\Exception $e) {
+			$thrown = true;
+			$this->assertInstanceOf(LockedException::class, $e);
+		}
+		$this->assertTrue($thrown, 'Exception was rethrown');
+
+		// clean shared lock
+		fclose($handle);
+
+		$this->assertNull($this->getFileLockType($view, 'test.txt'), 'File got unlocked');
+	}
+
 	/**
 	 * Test locks for fopen with fclose at the end
 	 *