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Date: Mon, 12 Mar 2018 15:06:12 +0100
From: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To: Kees Cook <keescook@...omium.org>
Cc: Joao Moreira <jmoreira@...e.de>, Greg KH <gregkh@...uxfoundation.org>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>, LKML
<linux-kernel@...r.kernel.org>, Daniel Micay <danielmicay@...il.com>,
linux-fbdev@...r.kernel.org
Subject: Re: [PATCH] vgacon: fix function prototypes
Hi,
On Saturday, March 10, 2018 07:27:21 AM Kees Cook wrote:
> On Fri, Mar 9, 2018 at 10:40 PM, Joao Moreira <jmoreira@...e.de> wrote:
> > It is possible to indirectly invoke functions with prototypes that do not
> > match those of the respectively used function pointers by using void types.
> > Despite widely used as a feature for relaxing function invocation, this
> > should be avoided when possible as it may prevent the use of heuristics
> > such as prototype matching-based Control-Flow Integrity, which can be used
> > to prevent ROP-based attacks.
> >
> > Given the above, the current efforts to improve the Linux security, and the
> > upcoming kernel support to compilers with CFI features, fix prototypes in
> > vgacon console driver.
> >
> > Another similar fix can be seen in [1].
> >
> > [1] https://android-review.googlesource.com/c/kernel/common/+/602010
> >
> > Signed-off-by: João Moreira <jmoreira@...e.de>
>
> Whoops, I missed this one. :) Thanks! Greg, do you need this resent
> directly to you?
I would prefer for drivers/video/console/ changes to go through
fbdev tree (like suggested by scripts/get_maintainers.pl)..
However since Greg has already merged your CFI patches:
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
> Acked-by: Kees Cook <keescook@...omium.org>
>
> -Kees
>
> > ---
> > drivers/video/console/vgacon.c | 18 +++++++++++++-----
> > 1 file changed, 13 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
> > index a17ba1465815..f00b630f6839 100644
> > --- a/drivers/video/console/vgacon.c
> > +++ b/drivers/video/console/vgacon.c
> > @@ -1407,21 +1407,29 @@ static bool vgacon_scroll(struct vc_data *c, unsigned int t, unsigned int b,
> > * The console `switch' structure for the VGA based console
> > */
> >
> > -static int vgacon_dummy(struct vc_data *c)
> > +static int vgacon_clear(struct vc_data *c)
> > {
> > return 0;
> > }
> >
> > -#define DUMMY (void *) vgacon_dummy
> > +static void vgacon_putc(struct vc_data *c, int a, int b, int d)
> > +{
> > + return;
> > +}
> > +
> > +static void vgacon_putcs(struct vc_data *c, ushort *s, int a, int b, int d)
> > +{
> > + return;
> > +}
> >
> > const struct consw vga_con = {
> > .owner = THIS_MODULE,
> > .con_startup = vgacon_startup,
> > .con_init = vgacon_init,
> > .con_deinit = vgacon_deinit,
> > - .con_clear = DUMMY,
> > - .con_putc = DUMMY,
> > - .con_putcs = DUMMY,
> > + .con_clear = vgacon_clear,
> > + .con_putc = vgacon_putc,
> > + .con_putcs = vgacon_putcs,
> > .con_cursor = vgacon_cursor,
> > .con_scroll = vgacon_scroll,
> > .con_switch = vgacon_switch,
> > --
> > 2.13.6
Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics
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