linux-kernel - Re: [PATCH] s390/mm: Fix in_atomic() handling in do_secure_storage

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Message-ID: <20250604194043.0ab9535e@p-imbrenda>
Date: Wed, 4 Jun 2025 19:40:43 +0200
From: Claudio Imbrenda <imbrenda@...ux.ibm.com>
To: Alexander Gordeev <agordeev@...ux.ibm.com>
Cc: Heiko Carstens <hca@...ux.ibm.com>, Janosch Frank
 <frankja@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Sven Schnelle <svens@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        kvm@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] s390/mm: Fix in_atomic() handling in
 do_secure_storage_access()

On Wed, 4 Jun 2025 19:29:31 +0200
Alexander Gordeev <agordeev@...ux.ibm.com> wrote:

> On Wed, Jun 04, 2025 at 06:48:55PM +0200, Claudio Imbrenda wrote:
> > > > @@ -441,6 +441,8 @@ void do_secure_storage_access(struct pt_regs *regs)
> > > >  		if (rc)
> > > >  			BUG();
> > > >  	} else {
> > > > +		if (faulthandler_disabled())
> > > > +			return handle_fault_error_nolock(regs, 0);
> > > >    
> > > 
> > > This could trigger WARN_ON_ONCE() in handle_fault_error_nolock():
> > > 
> > > 		if (WARN_ON_ONCE(!si_code))
> > > 			si_code = SEGV_MAPERR;
> > > 
> > > Would this warning be justified in this case (aka user_mode(regs) ==
> > > true)?  
> > 
> > I think so, because if we are in usermode, we should never trigger
> > faulthandler_disabled()  
> 
> I think I do not get you. We are in a system call and also in_atomic(),
> so faulthandler_disabled() is true and handle_fault_error_nolock(regs, 0)
> is called (above).

what is the psw in regs?
is it not the one that was being used when the exception was triggered?

> 
> >   
> > >   
> > > >  		mm = current->mm;
> > > >  		mmap_read_lock(mm);
> > > >  		vma = find_vma(mm, addr);