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From:   Matteo Croce <mcroce@redhat.com>
Date:   Tue, 26 Mar 2019 21:36:48 +0100
Message-ID: <CAGnkfhwtXdjaHFChFBMNiSnh+cpDRi=e20J0EZ039xWuRTcouQ@mail.gmail.com>
Subject: Re: [PATCH v2] x86/realmode: don't leak kernel addresses
To:     Borislav Petkov <bp@alien8.de>
Cc:     x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        lkml <linux-kernel@vger.kernel.org>
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On Tue, Mar 26, 2019 at 5:15 PM Borislav Petkov <bp@alien8.de> wrote:
>
> On Sun, Mar 24, 2019 at 08:05:04PM +0100, Matteo Croce wrote:
> > Since commit ad67b74d2469d9b8 ("printk: hash addresses printed with %p"),
> > at boot "____ptrval____" is printed instead of the trampoline addresses:
> >
> >     Base memory trampoline at [(____ptrval____)] 99000 size 24576
> >
> > Remove the address from the print as we don't want to leak kernel
> > addresses.
> >
> > Fixes: ad67b74d2469d9b8 ("printk: hash addresses printed with %p")
> > Signed-off-by: Matteo Croce <mcroce@redhat.com>
> > ---
> >  arch/x86/realmode/init.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c
> > index d10105825d57..d76a1380ec37 100644
> > --- a/arch/x86/realmode/init.c
> > +++ b/arch/x86/realmode/init.c
> > @@ -20,8 +20,8 @@ void __init set_real_mode_mem(phys_addr_t mem, size_t size)
> >       void *base = __va(mem);
> >
> >       real_mode_header = (struct real_mode_header *) base;
> > -     printk(KERN_DEBUG "Base memory trampoline at [%p] %llx size %zu\n",
> > -            base, (unsigned long long)mem, size);
> > +     printk(KERN_DEBUG "Base memory trampoline at %llx size %zu\n",
> > +            (unsigned long long)mem, size);
>
> In case this wasn't clear, please remove the whole printk. And don't
> forget to CC lkml on your submissions. CCed now.
>
> --
> Regards/Gruss,
>     Boris.
>
> Good mailing practices for 400: avoid top-posting and trim the reply.

Got it, sent a v3 with the printk removed.
Anyway, I wonder if we can remove the 'size' argument and/or moving
set_real_mode_mem() into realmode.h to have it inlined.
Or maybe it's not worth it.

Regards,
-- 
Matteo Croce
per aspera ad upstream