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

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Message-ID: <20250604184855.44793208@p-imbrenda>
Date: Wed, 4 Jun 2025 18:48:55 +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 18:27:49 +0200
Alexander Gordeev <agordeev@...ux.ibm.com> wrote:

> On Tue, Jun 03, 2025 at 03:49:36PM +0200, Heiko Carstens wrote:
> > diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
> > index 3829521450dd..e1ad05bfd28a 100644
> > --- a/arch/s390/mm/fault.c
> > +++ b/arch/s390/mm/fault.c
> > @@ -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()

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