linux-kernel - Re: [PATCH] rcu: kasan: record and print kvfree_call

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Date:   Fri, 20 Nov 2020 13:49:11 +0100
From:   Uladzislau Rezki <urezki@...il.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>,
        Zqiang <qiang.zhang@...driver.com>
Cc:     Uladzislau Rezki <urezki@...il.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>, rcu@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        kasan-dev <kasan-dev@...glegroups.com>
Subject: Re: [PATCH] rcu: kasan: record and print kvfree_call_rcu call stack

> On Fri, Nov 20, 2020 at 12:59 PM Uladzislau Rezki <urezki@...il.com> wrote:
> >
> > On Thu, Nov 19, 2020 at 01:49:34PM -0800, Paul E. McKenney wrote:
> > > On Wed, Nov 18, 2020 at 11:53:09AM +0800, qiang.zhang@...driver.com wrote:
> > > > From: Zqiang <qiang.zhang@...driver.com>
> > > >
> > > > Add kasan_record_aux_stack function for kvfree_call_rcu function to
> > > > record call stacks.
> > > >
> > > > Signed-off-by: Zqiang <qiang.zhang@...driver.com>
> > >
> > > Thank you, but this does not apply on the "dev" branch of the -rcu tree.
> > > See file:///home/git/kernel.org/rcutodo.html for more info.
> > >
> > > Adding others on CC who might have feedback on the general approach.
> > >
> > >                                                       Thanx, Paul
> > >
> > > > ---
> > > >  kernel/rcu/tree.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > > > index da3414522285..a252b2f0208d 100644
> > > > --- a/kernel/rcu/tree.c
> > > > +++ b/kernel/rcu/tree.c
> > > > @@ -3506,7 +3506,7 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
> > > >             success = true;
> > > >             goto unlock_return;
> > > >     }
> > > > -
> > > > +   kasan_record_aux_stack(ptr);
> > Is that save to invoke it on vmalloced ptr.?
> 
> Yes, kasan_record_aux_stack should figure it out itself.
> We call kasan_record_aux_stack on call_rcu as well, and rcu structs
> can be anywhere.
> See:
> https://elixir.bootlin.com/linux/v5.10-rc4/source/mm/kasan/generic.c#L335
>
Ah, i see the check. Just a minor comment, please also add a
clear comment about intention of doing such record.

Reviewed-by: Uladzislau Rezki (Sony) <urezki@...il.com>

Thanks.

--
Vlad Rezki