[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Thu, 5 May 2022 09:30:53 +0200
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Javier Martinez Canillas <javierm@...hat.com>,
linux-kernel@...r.kernel.org
Cc: linux-fbdev@...r.kernel.org,
Daniel Vetter <daniel.vetter@...ll.ch>,
Helge Deller <deller@....de>, dri-devel@...ts.freedesktop.org,
Peter Jones <pjones@...hat.com>
Subject: Re: [PATCH 3/3] fbdev/efifb: Cleanup fb_info in .fb_destroy rather
than .remove
Am 04.05.22 um 23:58 schrieb Javier Martinez Canillas:
> The driver is calling framebuffer_release() in its .remove callback, but
> this will cause the struct fb_info to be freed too early. Since it could
> be that a reference is still hold to it if user-space opened the fbdev.
>
> This would lead to a use-after-free error if the framebuffer device was
> unregistered but later a user-space process tries to close the fbdev fd.
>
> The correct thing to do is to only unregister the framebuffer in the
> driver's .remove callback, but do any cleanup in the fb_ops.fb_destroy.
>
> Suggested-by: Daniel Vetter <daniel.vetter@...ll.ch>
> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>
> ---
>
> drivers/video/fbdev/efifb.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
> index ea42ba6445b2..cfa3dc0b4eee 100644
> --- a/drivers/video/fbdev/efifb.c
> +++ b/drivers/video/fbdev/efifb.c
> @@ -243,6 +243,10 @@ static void efifb_show_boot_graphics(struct fb_info *info)
> static inline void efifb_show_boot_graphics(struct fb_info *info) {}
> #endif
>
> +/*
> + * fb_ops.fb_destroy is called by the last put_fb_info() call at the end
> + * of unregister_framebuffer() or fb_release(). Do any cleanup here.
> + */
> static void efifb_destroy(struct fb_info *info)
> {
> if (efifb_pci_dev)
> @@ -254,6 +258,9 @@ static void efifb_destroy(struct fb_info *info)
> else
> memunmap(info->screen_base);
> }
> +
> + framebuffer_release(info);
> +
> if (request_mem_succeeded)
> release_mem_region(info->apertures->ranges[0].base,
> info->apertures->ranges[0].size);
> @@ -620,9 +627,9 @@ static int efifb_remove(struct platform_device *pdev)
> {
> struct fb_info *info = platform_get_drvdata(pdev);
>
> + /* efifb_destroy takes care of info cleanup */
> unregister_framebuffer(info);
> sysfs_remove_groups(&pdev->dev.kobj, efifb_groups);
> - framebuffer_release(info);
>
> return 0;
> }
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
Download attachment "OpenPGP_signature" of type "application/pgp-signature" (841 bytes)
Powered by blists - more mailing lists