From 6b4737f4798507c8538ddff99927262a58b81911 Mon Sep 17 00:00:00 2001
From: lazerg <lazerg2@gmail.com>
Date: Tue, 3 Nov 2026 11:52:59 +0500
Subject: [PATCH] fix(lock): keep first saved TTL across nested shared locks

Assisted-by: ClaudeCode:claude-opus-5-5

Signed-off-by: lazerg <lazerg2@gmail.com>
---
 lib/private/Lock/MemcacheLockingProvider.php  | 10 ++--
 .../lib/Lock/MemcacheLockingProviderTest.php  | 56 +++++++++++++++++++
 2 files changed, 62 insertions(+), 4 deletions(-)

diff --git a/lib/private/Lock/MemcacheLockingProvider.php b/lib/private/Lock/MemcacheLockingProvider.php
index 51a3ca26ec764..8aba1d6ce659f 100644
--- a/lib/private/Lock/MemcacheLockingProvider.php
+++ b/lib/private/Lock/MemcacheLockingProvider.php
@@ -64,10 +64,12 @@ public function isLocked(string $path, int $type): bool {
 	public function acquireLock(string $path, int $type, ?string $readablePath = null): void {
 		if ($type === self::LOCK_SHARED) {
 			// save the old TTL to for `restoreTTL`
-			$this->oldTTLs[$path] = [
-				'ttl' => $this->getTTL($path),
-				'time' => $this->timeFactory->getTime()
-			];
+			if ($this->getOwnSharedLockCount($path) === 0) {
+				$this->oldTTLs[$path] = [
+					'ttl' => $this->getTTL($path),
+					'time' => $this->timeFactory->getTime()
+				];
+			}
 			if (!$this->memcache->inc($path)) {
 				throw new LockedException($path, null, $this->getExistingLockForException($path), $readablePath);
 			}
diff --git a/tests/lib/Lock/MemcacheLockingProviderTest.php b/tests/lib/Lock/MemcacheLockingProviderTest.php
index 492f474c33ced..3d7025b6e54e2 100644
--- a/tests/lib/Lock/MemcacheLockingProviderTest.php
+++ b/tests/lib/Lock/MemcacheLockingProviderTest.php
@@ -12,7 +12,9 @@
 use OC\Memcache\ArrayCache;
 use OCP\AppFramework\Utility\ITimeFactory;
 use OCP\IMemcache;
+use OCP\IMemcacheTTL;
 use OCP\Lock\ILockingProvider;
+use OCP\Lock\LockedException;
 use OCP\Server;
 
 class MemcacheLockingProviderTest extends LockingProvider {
@@ -21,6 +23,8 @@ class MemcacheLockingProviderTest extends LockingProvider {
 	 */
 	private $memcache;
 
+	private int $now = 0;
+
 	/**
 	 * @return ILockingProvider
 	 */
@@ -36,4 +40,56 @@ protected function tearDown(): void {
 		$this->memcache->clear();
 		parent::tearDown();
 	}
+
+	public function testFailedExclusiveLockRestoresTTLAfterNestedSharedLock(): void {
+		$timeFactory = $this->createMock(ITimeFactory::class);
+		$timeFactory->method('getTime')
+			->willReturnCallback(fn () => $this->now);
+		$memcache = new class($timeFactory) extends ArrayCache implements IMemcacheTTL {
+			private array $expires = [];
+
+			public function __construct(
+				private ITimeFactory $timeFactory,
+			) {
+				parent::__construct();
+			}
+
+			#[\Override]
+			public function setTTL(string $key, int $ttl) {
+				$this->expires[$key] = $this->timeFactory->getTime() + $ttl;
+			}
+
+			#[\Override]
+			public function getTTL(string $key): int|false {
+				return isset($this->expires[$key]) ? $this->expires[$key] - $this->timeFactory->getTime() : false;
+			}
+
+			#[\Override]
+			public function compareSetTTL(string $key, $value, int $ttl): bool {
+				if ($this->get($key) !== $value) {
+					return false;
+				}
+				$this->setTTL($key, $ttl);
+				return true;
+			}
+		};
+
+		$this->now = 1000;
+		$leaked = new MemcacheLockingProvider($memcache, $timeFactory);
+		$leaked->acquireLock('foo', ILockingProvider::LOCK_SHARED);
+
+		$this->now = 2000;
+		$provider = new MemcacheLockingProvider($memcache, $timeFactory);
+		$provider->acquireLock('foo', ILockingProvider::LOCK_SHARED);
+		$provider->acquireLock('foo', ILockingProvider::LOCK_SHARED);
+		$provider->releaseLock('foo', ILockingProvider::LOCK_SHARED);
+		try {
+			$provider->changeLock('foo', ILockingProvider::LOCK_EXCLUSIVE);
+			$this->fail('Expected LockedException');
+		} catch (LockedException) {
+		}
+		$provider->releaseLock('foo', ILockingProvider::LOCK_SHARED);
+
+		$this->assertEquals(2600, $memcache->getTTL('foo'));
+	}
 }