linux-kernel - Re: [PATCH v2 5/7] x86: plumb error code and fault address through to fault handlers

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Date:   Mon, 27 Aug 2018 21:25:44 +0200
From:   Jann Horn <jannh@...gle.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        tony.luck@...el.com, Borislav Petkov <bp@...en8.de>,
        kernel list <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>, linux-edac@...r.kernel.org
Subject: Re: [PATCH v2 5/7] x86: plumb error code and fault address through to
 fault handlers

On Mon, Aug 27, 2018 at 9:09 PM Andy Lutomirski <luto@...nel.org> wrote:
>
> On Mon, Aug 27, 2018 at 11:56 AM, Jann Horn <jannh@...gle.com> wrote:
> > This is preparation for looking at trap number and fault address in the
> > handlers for uaccess errors.
> > This patch should not change any behavior.
>
> Confused.  $SUBJECT says you're plumbing the error code through, and
> you are sort of doing it:
>
> > -int fixup_exception(struct pt_regs *regs, int trapnr)
> > +int fixup_exception(struct pt_regs *regs, int trapnr, unsigned long error_code,
> > +                   unsigned long fault_addr)
> >  {
>
> It's available here...
>
> >         const struct exception_table_entry *e;
> >         ex_handler_t handler;
> > @@ -202,7 +212,7 @@ int fixup_exception(struct pt_regs *regs, int trapnr)
> >                 return 0;
> >
> >         handler = ex_fixup_handler(e);
> > -       return handler(e, regs, trapnr);
> > +       return handler(e, regs, trapnr, fault_addr);
>
> ... but you don't pass it into the handlers.  Is this intentional?

Whoops. No, that's not intentional. I'll fix it up for the next version.