linux-kernel - [PATCH] futex: sync set the hash table slot

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Message-ID: <tencent_6B2EF84C8DE7C286F312E5C64889B9EEE806@qq.com>
Date: Mon,  2 Jun 2025 12:37:09 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+0a5079ee014f4b907817@...kaller.appspotmail.com
Cc: andrealmeid@...lia.com,
	dave@...olabs.net,
	dvhart@...radead.org,
	linux-kernel@...r.kernel.org,
	mingo@...hat.com,
	peterz@...radead.org,
	syzkaller-bugs@...glegroups.com,
	tglx@...utronix.de
Subject: [PATCH] futex: sync set the hash table slot

Prevent different processes from setting the hash table at the same
time to avoid hash table damage.

Reported-by: syzbot+0a5079ee014f4b907817@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=0a5079ee014f4b907817
Tested-by: syzbot+0a5079ee014f4b907817@...kaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@...com>
---
 kernel/futex/core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/futex/core.c b/kernel/futex/core.c
index 19a2c65f3d37..818dc082670f 100644
--- a/kernel/futex/core.c
+++ b/kernel/futex/core.c
@@ -1754,7 +1754,12 @@ int futex_hash_prctl(unsigned long arg2, unsigned long arg3, unsigned long arg4)
 			return -EINVAL;
 		if (arg4 & FH_FLAG_IMMUTABLE)
 			flags |= FH_IMMUTABLE;
+
+		static DEFINE_MUTEX(fha_syn);
+
+		mutex_lock(&fha_syn);
 		ret = futex_hash_allocate(arg3, flags);
+		mutex_unlock(&fha_syn);
 		break;
 
 	case PR_FUTEX_HASH_GET_SLOTS:
-- 
2.43.0