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Message-Id: <20240912113052.2904-1-hdanton@sina.com>
Date: Thu, 12 Sep 2024 19:30:52 +0800
From: Hillf Danton <hdanton@...a.com>
To: Frederic Weisbecker <frederic@...nel.org>
Cc: syzbot <syzbot+943d34fa3cf2191e3068@...kaller.appspotmail.com>,
linux-kernel@...r.kernel.org,
syzkaller-bugs@...glegroups.com,
Thomas Gleixner <tglx@...utronix.de>,
Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH] kthread: Unpark only parked kthreads (was Re: [syzbot] [wireguard?] WARNING in kthread_unpark (2))
On Wed, 11 Sep 2024 14:04:28 +0200 Frederic Weisbecker <frederic@...nel.org>
>
> Can you test the following?
> ---
One line is needed to feed syzbot including four parts, see below for an example
two keywords tree tag or commit
syz test upstream master
> From: Frederic Weisbecker <frederic@...nel.org>
> 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
> <TASK>
> 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
> </TASK>
>
> Fix this with skipping unecessary unparking while stopping a kthread.
>
> Reported-by: syzbot+943d34fa3cf2191e3068@...kaller.appspotmail.com
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
> ---
> 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 = to_kthread(k);
>
> + 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.
> --
> 2.46.0
#syz test upstream master
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -623,6 +623,8 @@ void kthread_unpark(struct task_struct *
{
struct kthread *kthread = to_kthread(k);
+ 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.
--
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