linux-kernel - Re: [syzbot] [wireless?] WARNING in kcov_remote

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Date: Thu, 28 Mar 2024 12:45:10 +0100
From: Johannes Berg <johannes@...solutions.net>
To: syzbot <syzbot+0438378d6f157baae1a2@...kaller.appspotmail.com>, 
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org, 
	netdev@...r.kernel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Cc: Andrey Konovalov <andreyknvl@...il.com>, Dmitry Vyukov
 <dvyukov@...gle.com>,  Aleksandr Nogikh <nogikh@...gle.com>
Subject: Re: [syzbot] [wireless?] WARNING in kcov_remote_start (3)

On Thu, 2024-03-28 at 04:00 -0700, syzbot wrote:
> 
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 2400 at kernel/kcov.c:860 kcov_remote_start+0x549/0x7e0 kernel/kcov.c:860

This is

        /*
         * Check that kcov_remote_start() is not called twice in background
         * threads nor called by user tasks (with enabled kcov).
         */
        mode = READ_ONCE(t->kcov_mode);
        if (WARN_ON(in_task() && kcov_mode_enabled(mode))) {
                local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
                return;
        }

but I have no idea what that even means?

> Workqueue: events_unbound cfg80211_wiphy_work
> RIP: 0010:kcov_remote_start+0x549/0x7e0 kernel/kcov.c:860
..
> Call Trace:
>  <TASK>
>  kcov_remote_start_common include/linux/kcov.h:48 [inline]
>  ieee80211_iface_work+0x21f/0xf10 net/mac80211/iface.c:1654
>  cfg80211_wiphy_work+0x221/0x260 net/wireless/core.c:437
>  process_one_work kernel/workqueue.c:3218 [inline]
>  process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3299
>  worker_thread+0x86d/0xd70 kernel/workqueue.c:3380

It's a worker thread. Was this not intended to be called in threads?

johannes