linux-kernel - Re: [PATCH 4.4 02/96] s390/runtime instrumention: fix possible memory corruption

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Date:   Wed, 6 Dec 2017 08:44:53 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Heiko Carstens <heiko.carstens@...ibm.com>
Cc:     Ben Hutchings <ben.hutchings@...ethink.co.uk>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH 4.4 02/96] s390/runtime instrumention: fix possible
 memory corruption

On Tue, Dec 05, 2017 at 07:15:34PM +0100, Heiko Carstens wrote:
> On Tue, Dec 05, 2017 at 06:08:47PM +0100, Greg Kroah-Hartman wrote:
> > On Tue, Dec 05, 2017 at 05:02:32PM +0000, Ben Hutchings wrote:
> > > On Tue, 2017-11-28 at 11:22 +0100, Greg Kroah-Hartman wrote:
> > > > 4.4-stable review patch.  If anyone has any objections, please let me know.
> > > > 
> > > > ------------------
> > > > 
> > > > From: Heiko Carstens <heiko.carstens@...ibm.com>
> > > > 
> > > > commit d6e646ad7cfa7034d280459b2b2546288f247144 upstream.
> > > [...]
> > > > --- a/arch/s390/kernel/runtime_instr.c
> > > > +++ b/arch/s390/kernel/runtime_instr.c
> > > > @@ -47,11 +47,13 @@ void exit_thread_runtime_instr(void)
> > > >  {
> > > >  	struct task_struct *task = current;
> > > >  
> > > > +	preempt_disable();
> > > >  	if (!task->thread.ri_cb)
> > > >  		return;
> > > 
> > > This return path now leaves preemption disabled.  This seems to have
> > > been fixed upstream by commit 8d9047f8b967 "s390/runtime
> > > instrumentation: simplify task exit handling".
> > 
> > "simplify" doesn't seem to imply "fixes a bug" :)
> 
> Indeed ;) That where two subsequent patches, but incorrectly split by me...
> 
> > Heiko, should I also queue this patch up?
> 
> Yes, please.

It doesn't apply to 4.9-stable or 4.4-stable, can you provide a working
backport?

thanks,

greg k-h