Message-ID: <4bca96c7614eefa5e46959dc46bcb25165fd28cf.camel@gmail.com>
Subject: Re: [PATCH v2] fbdev: Fix invalid page access after closing
 deferred I/O devices
From:   Miko Larsson <mikoxyzzz@gmail.com>
To:     Takashi Iwai <tiwai@suse.de>, Helge Deller <deller@gmx.de>
Cc:     linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org,
        Patrik Jakobsson <pjakobsson@suse.de>,
        Thomas Zimmermann <tzimmermann@suse.de>
Date:   Sun, 29 Jan 2023 12:33:50 +0100
In-Reply-To: <20230129082856.22113-1-tiwai@suse.de>
References: <20230129082856.22113-1-tiwai@suse.de>
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On Sun, 2023-01-29 at 09:28 +0100, Takashi Iwai wrote:
> When a fbdev with deferred I/O is once opened and closed, the dirty
> pages still remain queued in the pageref list, and eventually later
> those may be processed in the delayed work.=C2=A0 This may lead to a
> corruption of pages, hitting an Oops.
>=20
> This patch makes sure to cancel the delayed work and clean up the
> pageref list at closing the device for addressing the bug.=C2=A0 A part o=
f
> the cleanup code is factored out as a new helper function that is
> called from the common fb_release().
>=20
> Reviewed-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> ---
> v1->v2: Fix build error without CONFIG_FB_DEFERRED_IO
>=20
> =C2=A0drivers/video/fbdev/core/fb_defio.c | 10 +++++++++-
> =C2=A0drivers/video/fbdev/core/fbmem.c=C2=A0=C2=A0=C2=A0 |=C2=A0 4 ++++
> =C2=A0include/linux/fb.h=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 |=C2=A0 1 +
> =C2=A03 files changed, 14 insertions(+), 1 deletion(-)
>=20
> diff --git a/drivers/video/fbdev/core/fb_defio.c
> b/drivers/video/fbdev/core/fb_defio.c
> index c730253ab85c..583cbcf09446 100644
> --- a/drivers/video/fbdev/core/fb_defio.c
> +++ b/drivers/video/fbdev/core/fb_defio.c
> @@ -313,7 +313,7 @@ void fb_deferred_io_open(struct fb_info *info,
> =C2=A0}
> =C2=A0EXPORT_SYMBOL_GPL(fb_deferred_io_open);
> =C2=A0
> -void fb_deferred_io_cleanup(struct fb_info *info)
> +void fb_deferred_io_release(struct fb_info *info)
> =C2=A0{
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0struct fb_deferred_io *fb=
defio =3D info->fbdefio;
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0struct page *page;
> @@ -327,6 +327,14 @@ void fb_deferred_io_cleanup(struct fb_info
> *info)
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0page =3D fb_deferred_io_page(info, i);
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0page->mapping =3D NULL;
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0}
> +}
> +EXPORT_SYMBOL_GPL(fb_deferred_io_release);
> +
> +void fb_deferred_io_cleanup(struct fb_info *info)
> +{
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0struct fb_deferred_io *fbdefio=
 =3D info->fbdefio;
> +
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0fb_deferred_io_release(info);
> =C2=A0
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0kvfree(info->pagerefs);
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0mutex_destroy(&fbdefio->l=
ock);
> diff --git a/drivers/video/fbdev/core/fbmem.c
> b/drivers/video/fbdev/core/fbmem.c
> index 3a6c8458eb8d..ab3545a00abc 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -1454,6 +1454,10 @@ __releases(&info->lock)
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0struct fb_info * const in=
fo =3D file->private_data;
> =C2=A0
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0lock_fb_info(info);
> +#if IS_ENABLED(CONFIG_FB_DEFERRED_IO)
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (info->fbdefio)
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0fb_deferred_io_release(info);
> +#endif
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (info->fbops->fb_relea=
se)
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0info->fbops->fb_release(info,1);
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0module_put(info->fbops->o=
wner);
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index 96b96323e9cb..73eb1f85ea8e 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -662,6 +662,7 @@ extern int=C2=A0 fb_deferred_io_init(struct fb_info
> *info);
> =C2=A0extern void fb_deferred_io_open(struct fb_info *info,
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0struct inode *inode,
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0struct file *file);
> +extern void fb_deferred_io_release(struct fb_info *info);
> =C2=A0extern void fb_deferred_io_cleanup(struct fb_info *info);
> =C2=A0extern int fb_deferred_io_fsync(struct file *file, loff_t start,
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0loff_t end, int datasync);

Tested-by: Miko Larsson <mikoxyzzz@gmail.com>
--=20
~miko