linux-kernel - Re: [Linux-kernel-mentees] [PATCH] drm/bufs: Prevent kernel-infoleak in copy_one

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Date:   Tue, 28 Jul 2020 07:15:27 -0400
From:   Peilin Ye <yepeilin.cs@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Linux-kernel-mentees] [PATCH] drm/bufs: Prevent kernel-infoleak
 in copy_one_buf()

On Tue, Jul 28, 2020 at 10:11:09AM +0200, Arnd Bergmann wrote:
> On Tue, Jul 28, 2020 at 3:45 AM Peilin Ye <yepeilin.cs@...il.com> wrote:
> >
> > copy_one_buf() is copying uninitialized stack memory to userspace due to
> > the compiler not initializing holes in statically allocated structures.
> > Fix it by initializing `v` with memset().
> 
> I would add 'potentially' somewhere in that description: it is architecture
> dependent whether there are holes in this structure as 'enum' types
> and 'long' are both dependent on the ABI, and even if there is a hole,
> it is undefined behavior whether the hold gets initialized.

I see. I will fix that up. Thank you for the advice!

Peilin Ye

> Other than that, the patch looks good.
> 
> > Cc: stable@...r.kernel.org
> > Fixes: 5c7640ab6258 ("switch compat_drm_infobufs() to drm_ioctl_kernel()")
> > Suggested-by: Dan Carpenter <dan.carpenter@...cle.com>
> > Signed-off-by: Peilin Ye <yepeilin.cs@...il.com>
> 
> Acked-by: Arnd Bergmann <arnd@...db.de>