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

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Message-ID: <aECCe9bIZORv+yef@li-008a6a4c-3549-11b2-a85c-c5cc2836eea2.ibm.com>
Date: Wed, 4 Jun 2025 19:29:31 +0200
From: Alexander Gordeev <agordeev@...ux.ibm.com>
To: Claudio Imbrenda <imbrenda@...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, 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).

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