linux-kernel - Re: mmotm 2019-08-27-20-39 uploaded (objtool: xen)

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Date:   Wed, 28 Aug 2019 15:01:34 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     akpm@...ux-foundation.org, broonie@...nel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-next@...r.kernel.org, mhocko@...e.cz,
        mm-commits@...r.kernel.org, sfr@...b.auug.org.au,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: mmotm 2019-08-27-20-39 uploaded (objtool: xen)

On Wed, Aug 28, 2019 at 10:56:25AM -0700, Randy Dunlap wrote:
> >> drivers/xen/gntdev.o: warning: objtool: gntdev_copy()+0x229: call to __ubsan_handle_out_of_bounds() with UACCESS enabled
> > 
> > Easy one :-)
> > 
> > diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> > index 0c8e17f946cd..6a935ab93149 100644
> > --- a/tools/objtool/check.c
> > +++ b/tools/objtool/check.c
> > @@ -483,6 +483,7 @@ static const char *uaccess_safe_builtin[] = {
> >  	"ubsan_type_mismatch_common",
> >  	"__ubsan_handle_type_mismatch",
> >  	"__ubsan_handle_type_mismatch_v1",
> > +	"__ubsan_handle_out_of_bounds",
> >  	/* misc */
> >  	"csum_partial_copy_generic",
> >  	"__memcpy_mcsafe",
> > 
> 
> 
> then I get this one:
> 
> lib/ubsan.o: warning: objtool: __ubsan_handle_out_of_bounds()+0x5d: call to ubsan_prologue() with UACCESS enabled

And of course I jinxed it by calling it easy.

Peter, how do you want to handle this?

Should we just disable UACCESS checking in lib/ubsan.c?

-- 
Josh