fix: unlock mailboxes after OOM

Signed-off-by: Christoph Wurst <1374172+ChristophWurst@users.noreply.github.com>

Author: ChristophWurst

lib/Service/Sync/ImapToDbSynchronizer.php

@@ -43,6 +43,7 @@
 use function array_chunk;
 use function array_filter;
 use function array_map;
+use function register_shutdown_function;
 use function sprintf;
 
 class ImapToDbSynchronizer {
@@ -214,6 +215,14 @@ public function sync(Account $account,
 		?array $knownUids = null,
 		bool $force = false,
 		bool $batchSync = false): bool {
+		/*
+		 * Reserve for unlocking
+		 *
+		 * Important: reserve early to avoid OOM after locking but before the
+		 * shutdown handler registration
+		 */
+		$oomBuffer = str_repeat(' ', 1024 * 1024);
+
 		$rebuildThreads = true;
 		if ($mailbox->getSelectable() === false) {
 			return $rebuildThreads;
@@ -249,6 +258,11 @@ public function sync(Account $account,
 			$this->mailboxMapper->lockForVanishedSync($mailbox);
 		}
 
+		register_shutdown_function(function () use ($force, $criteria, $logger, $mailbox, &$oomBuffer) {
+			unset($oomBuffer);
+			$this->unlockMailbox($force, $criteria, $logger, $mailbox);
+		});
+
 		try {
 			if ($force
 				|| $mailbox->getSyncNewToken() === null
@@ -281,18 +295,7 @@ public function sync(Account $account,
 		} catch (Throwable $e) {
 			throw new ServiceException('Sync failed for ' . $account->getId() . ':' . $mailbox->getName() . ': ' . $e->getMessage(), 0, $e);
 		} finally {
-			if ($force || ($criteria & Horde_Imap_Client::SYNC_VANISHEDUIDS)) {
-				$logger->debug('Unlocking mailbox ' . $mailbox->getId() . ' from vanished messages sync');
-				$this->mailboxMapper->unlockFromVanishedSync($mailbox);
-			}
-			if ($force || ($criteria & Horde_Imap_Client::SYNC_FLAGSUIDS)) {
-				$logger->debug('Unlocking mailbox ' . $mailbox->getId() . ' from changed messages sync');
-				$this->mailboxMapper->unlockFromChangedSync($mailbox);
-			}
-			if ($force || ($criteria & Horde_Imap_Client::SYNC_NEWMSGSUIDS)) {
-				$logger->debug('Unlocking mailbox ' . $mailbox->getId() . ' from new messages sync');
-				$this->mailboxMapper->unlockFromNewSync($mailbox);
-			}
+			$this->unlockMailbox($force, $criteria, $logger, $mailbox);
 		}
 
 		if (!$batchSync) {
@@ -308,6 +311,24 @@ public function sync(Account $account,
 		return $rebuildThreads;
 	}
 
+	private function unlockMailbox(bool $force, int $criteria, LoggerInterface $logger, Mailbox $mailbox): void {
+		if (($force || ($criteria & Horde_Imap_Client::SYNC_VANISHEDUIDS))
+			&& $mailbox->getSyncVanishedLock() !== null) {
+			$logger->debug('Unlocking mailbox ' . $mailbox->getId() . ' from vanished messages sync');
+			$this->mailboxMapper->unlockFromVanishedSync($mailbox);
+		}
+		if (($force || ($criteria & Horde_Imap_Client::SYNC_FLAGSUIDS))
+			&& $mailbox->getSyncChangedLock() !== null) {
+			$logger->debug('Unlocking mailbox ' . $mailbox->getId() . ' from changed messages sync');
+			$this->mailboxMapper->unlockFromChangedSync($mailbox);
+		}
+		if (($force || ($criteria & Horde_Imap_Client::SYNC_NEWMSGSUIDS))
+			&& $mailbox->getSyncNewLock() !== null) {
+			$logger->debug('Unlocking mailbox ' . $mailbox->getId() . ' from new messages sync');
+			$this->mailboxMapper->unlockFromNewSync($mailbox);
+		}
+	}
+
 	/**
 	 * @throws ServiceException
 	 * @throws IncompleteSyncException