From b58e8a129d62634e90080e6f89a0cf9d91361c0c Mon Sep 17 00:00:00 2001
From: Jamie Liu <jamieliu@google.com>
Date: Fri, 7 Jun 2024 09:27:41 -0700
Subject: [PATCH] futex: add missing locking in lockBuckets()

This was incorrectly dropped in cl/491486620.

PiperOrigin-RevId: 641272091
---
 pkg/sentry/kernel/futex/futex.go | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/pkg/sentry/kernel/futex/futex.go b/pkg/sentry/kernel/futex/futex.go
index d2b3eb8e4..c30d30172 100644
--- a/pkg/sentry/kernel/futex/futex.go
+++ b/pkg/sentry/kernel/futex/futex.go
@@ -453,7 +453,8 @@ func (m *Manager) lockBuckets(k1, k2 *Key) (b1, b2, lockedFirst, lockedSecond *b
 		b1.mu.NestedLock(futexBucketLockB)
 		return b1, b2, b2, b1
 	}
-	return b1, b2, nil, nil // +checklocksforce
+	b1.mu.Lock()
+	return b1, b2, b1, nil // +checklocksforce
 }
 
 // unlockBuckets unlocks two buckets.
@@ -463,10 +464,7 @@ func (m *Manager) unlockBuckets(lockedFirst, lockedSecond *bucket) {
 	if lockedSecond != nil {
 		lockedSecond.mu.NestedUnlock(futexBucketLockB)
 	}
-	if lockedFirst != nil && lockedFirst != lockedSecond {
-		lockedFirst.mu.Unlock()
-	}
-	return
+	lockedFirst.mu.Unlock()
 }
 
 // Wake wakes up to n waiters matching the bitmask on the given addr.