From nobody Sat Nov 30 05:49:37 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 E8B3351C4A for ; Wed, 11 Sep 2024 12:04:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726056272; cv=none; b=qsc23rf4wiaiQjX8sn33zmd42oBwI8vDfxHitrTm6S7GdlLAKXlWBKtd0Ti1oCyBgx0G0JyzdF5ORrhSane7YhO6W09KUBUdJl/3jIeVqaMOG8olWhGMrfx5Ges3tB9ZOi9m8h3IqRbfFGZB0uXrjfjjqarMOmCxU2bKCHESpdI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726056272; c=relaxed/simple; bh=BrvCDT4TB0sx1BI3jg+JNhXoijBqn8lODDE+FwuTf9A=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KS3rj01DA43242M7dy5F2rzcCBEEj7ktacmGSYB4qUACCpHKr73KZlgvoR8Gxo/GYzZSc8Rwqu/0aGKXnfpSiF8+898R/cHS9BqasLSjL/dnudhbxza+9tL6Zo/ZW8fbnSckKopgD8K2HWifvVdc5NYSB6Us/pjddeXg4f5oaJk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WbaoNNZy; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="WbaoNNZy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2C134C4CEC5; Wed, 11 Sep 2024 12:04:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1726056271; bh=BrvCDT4TB0sx1BI3jg+JNhXoijBqn8lODDE+FwuTf9A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WbaoNNZyc2VDdC4cYHG62nVDHWyogYtH+EwSEp+XXn1QGJ3BZcSHXyHeKKu4pem49 sJo3ahp8hFo+mrmW6C9tJC0voh5NBFr/rJgUkGbFWuJJ6DiG0ai8xGtsA44Dtm0oLP 6oO+h6PkIrP3pvWf9CpQQ+awSck2Mgi1hSEBMfWBzsBsYbBguMZAOmjnU68co1QZs8 lqSSdFIHjzbO7to2uRsySVFfFVYlFl7g9ZnVeDt07BW4EQ6l+UjqluGZgJp4G6rtsy a6ZhKb01EdM04nIggXhXg6NCwUkkfiMtDPwNxmgVJnm7M+ZltBzOes09FIgur1vXTc PpjBlzp/7HSiw== Date: Wed, 11 Sep 2024 14:04:28 +0200 From: Frederic Weisbecker To: syzbot Cc: hdanton@sina.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, Thomas Gleixner , Tejun Heo Subject: [PATCH] kthread: Unpark only parked kthreads (was Re: [syzbot] [wireguard?] WARNING in kthread_unpark (2)) Message-ID: References: <20240731110501.2425-1-hdanton@sina.com> <000000000000af4044061e89668a@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <000000000000af4044061e89668a@google.com> Content-Type: text/plain; charset="utf-8" Le Wed, Jul 31, 2024 at 04:29:02AM -0700, syzbot a =C3=A9crit : > Hello, >=20 > syzbot has tested the proposed patch and the reproducer did not trigger a= ny issue: >=20 > Reported-by: syzbot+943d34fa3cf2191e3068@syzkaller.appspotmail.com > Tested-by: syzbot+943d34fa3cf2191e3068@syzkaller.appspotmail.com >=20 > Tested on: >=20 > commit: dc1c8034 minmax: simplify min()/max()/clamp() implemen.. > git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/li= nux.git > console output: https://syzkaller.appspot.com/x/log.txt?x=3D1264b511980000 > kernel config: https://syzkaller.appspot.com/x/.config?x=3D2258b49cd9b33= 9fa > dashboard link: https://syzkaller.appspot.com/bug?extid=3D943d34fa3cf2191= e3068 > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Deb= ian) 2.40 > patch: https://syzkaller.appspot.com/x/patch.diff?x=3D10fe991198= 0000 >=20 > Note: testing is done by a robot and is best-effort only. >=20 The problem is in the kthread code. kthread_stop() seem to assume that the target is parked and since kthread_stop() is seldom called on per-cpu kthreads (smpboot_unregister_percpu_thread() doesn't have any user yet), th= is went unnoticed until workqueue happened to do it. Can you test the following? Reported-by: syzbot+943d34fa3cf2191e3068@syzkaller.appspotmail.com Suggested-by: Thomas Gleixner Tested-by: syzbot+943d34fa3cf2191e3068@syzkaller.appspotmail.com --- From: Frederic Weisbecker Date: Tue, 10 Sep 2024 22:10:19 +0200 Subject: [PATCH] kthread: Unpark only parked kthreads Calling into kthread unparking unconditionally is mostly harmless when the kthread is already unparked. The wake up is then simply ignored because the target is not in TASK_PARKED state. However if the kthread is per CPU, the wake up is preceded by a call to kthread_bind() which expects the task to be inactive and in TASK_PARKED state, which obviously isn't the case if it is unparked. As a result, calling kthread_stop() on an unparked per-cpu kthread triggers such a warning: WARNING: CPU: 0 PID: 11 at kernel/kthread.c:525 __kthread_bind_mask kernel= /kthread.c:525 kthread_stop+0x17a/0x630 kernel/kthread.c:707 destroy_workqueue+0x136/0xc40 kernel/workqueue.c:5810 wg_destruct+0x1e2/0x2e0 drivers/net/wireguard/device.c:257 netdev_run_todo+0xe1a/0x1000 net/core/dev.c:10693 default_device_exit_batch+0xa14/0xa90 net/core/dev.c:11769 ops_exit_list net/core/net_namespace.c:178 [inline] cleanup_net+0x89d/0xcc0 net/core/net_namespace.c:640 process_one_work kernel/workqueue.c:3231 [inline] process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312 worker_thread+0x86d/0xd70 kernel/workqueue.c:3393 kthread+0x2f0/0x390 kernel/kthread.c:389 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 Fix this with skipping unecessary unparking while stopping a kthread. Reported-by: syzbot+943d34fa3cf2191e3068@syzkaller.appspotmail.com Suggested-by: Thomas Gleixner Signed-off-by: Frederic Weisbecker --- kernel/kthread.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/kthread.c b/kernel/kthread.c index f7be976ff88a..5e2ba556aba8 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -623,6 +623,8 @@ void kthread_unpark(struct task_struct *k) { struct kthread *kthread =3D to_kthread(k); =20 + if (!test_bit(KTHREAD_SHOULD_PARK, &kthread->flags)) + return; /* * Newly created kthread was parked when the CPU was offline. * The binding was lost and we need to set it again. --=20 2.46.0