Re: [PATCH RFC 4/4] m68k equivalent of 26178ec11ef3 "x86: mm: consolidate VM_FAULT_RETRY handling" If e.g. get_user() triggers a page fault and a fatal signal is caught, we might end up with handle_mm_fault() returning VM_FAULT_RETRY and not doing anything to page tables. In such case we must *not* return to the faulting insn - that would repeat the entire thing without making any progress; what we need instead is to treat that as failed (user) memory access.

[Michael Schmitz <schmitzmic@xxxxxxxxx>]

Hi Adrian,

Am 05.02.2024 um 18:32 schrieb John Paul Adrian Glaubitz:
> Hi Michael,
>
> On Mon, 2024-02-05 at 08:21 +1300, Michael Schmitz wrote:
> > From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> >
> > MSch: v4.4 backport compile errors fixes.
> >
> > Tested-by: Finn Thain <fthain@xxxxxxxxxxxxxx>
> > Tested-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> > Acked-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> > Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Michael Schmitz <schmitzmic@xxxxxxxxx>
> > ---
> >  arch/m68k/mm/fault.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/m68k/mm/fault.c b/arch/m68k/mm/fault.c
> > index 6a94cdd0c830..f94df64c3784 100644
> > --- a/arch/m68k/mm/fault.c
> > +++ b/arch/m68k/mm/fault.c
> > @@ -139,8 +139,11 @@ good_area:
> >  	fault = handle_mm_fault(mm, vma, address, flags);
> >  	pr_debug("handle_mm_fault returns %d\n", fault);
> >
> > -	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
> > +	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) {
> > +		if (!user_mode(regs))
> > +			goto no_context;
> >  		return 0;
> > +	}
> >
> >  	if (unlikely(fault & VM_FAULT_ERROR)) {
> >  		if (fault & VM_FAULT_OOM)
>
> That subject looks like it contains the long description which should go
> into the patch instead.

Yep - I fat-fingered editing the commit message there. Thanks for spotting!

Fixed in v2.

	Michael

> Adrian