From nobody Thu Dec 18 00:13:12 2025 Received: from mta-64-225.siemens.flowmailer.net (mta-64-225.siemens.flowmailer.net [185.136.64.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A1D112EB1F for ; Thu, 5 Dec 2024 17:43:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.136.64.225 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733420627; cv=none; b=ZuFGqIAwqZnRnrKrqtDKlvnf04r78gFcidRQU+pWSCnHjHB+84mXYp+HqRJz5KvAlmgLZL/Fn80irkSjWhZVQJ5MIQZ4hZ6FAZoPt35nlyJFr+AOtNbB8FTSERCLe5g+aDWn0kdM9w6frNaF/vdVCjq1qxcoJ3kWM+yJlfdzz2U= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733420627; c=relaxed/simple; bh=77dDWmhz9+vNNVwfh+cDg6E6bZYQGGhWOkzcSD89/no=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=ZmCaZClPeiZBpEKlMG2BLEbZVy5DvwzJCnONoOIgU2G5YdqAxAyNlLIT4dLweuomg445xml/K/fiXCvsnLETFO0gcZn4QrvpBOfDKcyKXmc/p5k0otcwoTwObsyHLO9WHDgNC3r7k0RHoAsxVpyZhAHISyZli2JZ6halM9s+akY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=siemens.com; spf=pass smtp.mailfrom=rts-flowmailer.siemens.com; dkim=pass (2048-bit key) header.d=siemens.com header.i=alexander.sverdlin@siemens.com header.b=UoKgMQCK; arc=none smtp.client-ip=185.136.64.225 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=siemens.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=rts-flowmailer.siemens.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=siemens.com header.i=alexander.sverdlin@siemens.com header.b="UoKgMQCK" Received: by mta-64-225.siemens.flowmailer.net with ESMTPSA id 20241205170322a7db41e085103b262e for ; Thu, 05 Dec 2024 18:03:22 +0100 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; s=fm2; d=siemens.com; i=alexander.sverdlin@siemens.com; h=Date:From:Subject:To:Message-ID:MIME-Version:Content-Type:Content-Transfer-Encoding:Cc; bh=ziJSG6ctVi3hXuBtO97gjLaanzOcTvctskZW8qKtFqg=; b=UoKgMQCK3OZnoNoxk1GJ3f5UMqi0wKd5Hgy8yFKdTqcvOeGom2RqUa9OhYb9YHhH/JYK8J Ylhg5cCoSgtYoEnn/xC0Ucs+AEliU14rPmumoJizbabCyteDhx0FzLQSYs+e6c7gjNsEkhwi KqiGfTN21mGjeUOVzBT6RzWxDCjjfbld3kIZ60KCZX1HGfqwb6Ymou+DamEhygZHCPk+gv+b QpkNSXuTBD2ijFCTQZbgPLh8s5h9q/7vmrHAKm70ggGDrZz3Ie3NMklk/bL0sXIe3WqbqkR3 g1LQdlHHlrfBNtYT4yi5sRggJT5SsfAYJjG3rhWgOenG1K+U26ggMYwg==; From: "A. Sverdlin" To: Marco Elver , linux-kernel@vger.kernel.org Cc: Alexander Sverdlin , Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long , Boqun Feng , "Paul E . McKenney" , Adrian Freihofer Subject: [PATCH] locking/spinlock/debug: Fix data-race in do_raw_write_lock Date: Thu, 5 Dec 2024 18:01:29 +0100 Message-ID: <20241205170143.4105094-1-alexander.sverdlin@siemens.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Flowmailer-Platform: Siemens Feedback-ID: 519:519-456497:519-21489:flowmailer Content-Type: text/plain; charset="utf-8" From: Alexander Sverdlin KCSAN reports: BUG: KCSAN: data-race in do_raw_write_lock / do_raw_write_lock write (marked) to 0xffff800009cf504c of 4 bytes by task 1102 on cpu 1: do_raw_write_lock+0x120/0x204 _raw_write_lock_irq do_exit call_usermodehelper_exec_async ret_from_fork read to 0xffff800009cf504c of 4 bytes by task 1103 on cpu 0: do_raw_write_lock+0x88/0x204 _raw_write_lock_irq do_exit call_usermodehelper_exec_async ret_from_fork value changed: 0xffffffff -> 0x00000001 Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 1103 Comm: kworker/u4:1 6.1.111 Commit 1a365e822372 ("locking/spinlock/debug: Fix various data races") has adressed most of these races, but seems to be not consistent/not complete. From do_raw_write_lock() only debug_write_lock_after() part has been converted to WRITE_ONCE(), but not debug_write_lock_before() part. Do it now. Fixes: 1a365e822372 ("locking/spinlock/debug: Fix various data races") Reported-by: Adrian Freihofer Signed-off-by: Alexander Sverdlin Acked-by: Waiman Long --- There are still some inconsistencies remaining IMO: - lock->magic is sometimes accessed with READ_ONCE() even though it's only being plain-written; - debug_spin_unlock() and debug_write_unlock() both do WRITE_ONCE() on lock->owner and lock->owner_cpu, but examine them with plain read accesses. kernel/locking/spinlock_debug.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/locking/spinlock_debug.c b/kernel/locking/spinlock_debu= g.c index 87b03d2e41dbb..2338b3adfb55f 100644 --- a/kernel/locking/spinlock_debug.c +++ b/kernel/locking/spinlock_debug.c @@ -184,8 +184,8 @@ void do_raw_read_unlock(rwlock_t *lock) static inline void debug_write_lock_before(rwlock_t *lock) { RWLOCK_BUG_ON(lock->magic !=3D RWLOCK_MAGIC, lock, "bad magic"); - RWLOCK_BUG_ON(lock->owner =3D=3D current, lock, "recursion"); - RWLOCK_BUG_ON(lock->owner_cpu =3D=3D raw_smp_processor_id(), + RWLOCK_BUG_ON(READ_ONCE(lock->owner) =3D=3D current, lock, "recursion"); + RWLOCK_BUG_ON(READ_ONCE(lock->owner_cpu) =3D=3D raw_smp_processor_id(), lock, "cpu recursion"); } =20 --=20 2.47.1