Re: [syzbot] [bpf?] possible deadlock in kvfree_call_rcu

From: Uladzislau Rezki <urezki@gmail.com>
To: Hillf Danton <hdanton@sina.com>
Cc: Uladzislau Rezki <urezki@gmail.com>,
	syzbot <syzbot+1fa663a2100308ab6eab@syzkaller.appspotmail.com>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [bpf?] possible deadlock in kvfree_call_rcu
Date: Sun, 31 Mar 2024 09:25:56 +0200	[thread overview]
Message-ID: <ZgkQBA-Lsk9mxZJ3@pc636> (raw)
In-Reply-To: <20240331062314.3394-1-hdanton@sina.com>

On Sun, Mar 31, 2024 at 02:23:14PM +0800, Hillf Danton wrote:
> On Sat, 30 Mar 2024 18:55:41 +0100 Uladzislau Rezki <urezki@gmail.com>
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index d9642dd06c25..8867aac3668c 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -3467,19 +3467,19 @@ void kvfree_call_rcu(struct rcu_head *head, void *ptr)
> >  	 */
> >  	kmemleak_ignore(ptr);
> >  
> > -	// Set timer to drain after KFREE_DRAIN_JIFFIES.
> > -	if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING)
> > -		schedule_delayed_monitor_work(krcp);
> > -
> 
> This is not enough at least WRT run_page_cache_worker() [1]
> 
> [1] https://lore.kernel.org/lkml/0000000000007a44120614e27cb7@google.com/
> 
page-cache-worker should be move out of the krcp-lock also. I will
update the patch.

--
Uladzislau Rezki