[PATCH] fbdev: efifb: Fix a use-after-free due early fb_info cleanup

Commit d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather
than .remove") attempted to fix a use-after-free error due driver freeing
the fb_info in the .remove handler instead of doing it in .fb_destroy.

But ironically that change introduced yet another use-after-free since the
fb_info was still used after the free.

This should fix for good by freeing the fb_info at the end of the handler.

Fixes: d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather than .remove")
Reported-by: Ville Syrjälä <redacted>
Reported-by: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
---

 drivers/video/fbdev/efifb.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
index cfa3dc0b4eee..b3d5f884c544 100644
--- a/drivers/video/fbdev/efifb.c
+++ b/drivers/video/fbdev/efifb.c

@@ -259,12 +259,12 @@ static void efifb_destroy(struct fb_info *info)
 			memunmap(info->screen_base);
 	}
 
-	framebuffer_release(info);
-
 	if (request_mem_succeeded)
 		release_mem_region(info->apertures->ranges[0].base,
 				   info->apertures->ranges[0].size);
 	fb_dealloc_cmap(&info->cmap);
+
+	framebuffer_release(info);
 }
 
 static const struct fb_ops efifb_ops = {

-- 
2.35.1

Am 06.05.22 um 15:22 schrieb Javier Martinez Canillas:

Commit d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather
than .remove") attempted to fix a use-after-free error due driver freeing
the fb_info in the .remove handler instead of doing it in .fb_destroy.

But ironically that change introduced yet another use-after-free since the
fb_info was still used after the free.

This should fix for good by freeing the fb_info at the end of the handler.

Fixes: d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather than .remove")
Reported-by: Ville Syrjälä <redacted>
Reported-by: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>

Reviewed-by: Thomas Zimmermann <redacted>

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

Hi Javier,

On Fri, May 06, 2022 at 03:22:25PM +0200, Javier Martinez Canillas wrote:

Commit d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather
than .remove") attempted to fix a use-after-free error due driver freeing
the fb_info in the .remove handler instead of doing it in .fb_destroy.

But ironically that change introduced yet another use-after-free since the
fb_info was still used after the free.

This should fix for good by freeing the fb_info at the end of the handler.

Fixes: d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather than .remove")
Reported-by: Ville Syrjälä <redacted>
Reported-by: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>

Reviewed-by: Andi Shyti <redacted>

Andi

On 06.05.2022 15:22, Javier Martinez Canillas wrote:

Commit d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather
than .remove") attempted to fix a use-after-free error due driver freeing
the fb_info in the .remove handler instead of doing it in .fb_destroy.

But ironically that change introduced yet another use-after-free since the
fb_info was still used after the free.

This should fix for good by freeing the fb_info at the end of the handler.

Fixes: d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather than .remove")
Reported-by: Ville Syrjälä <redacted>
Reported-by: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
---

Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>

Regards
Andrzej

On Fri, May 06, 2022 at 03:22:25PM +0200, Javier Martinez Canillas wrote:

Commit d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather
than .remove") attempted to fix a use-after-free error due driver freeing
the fb_info in the .remove handler instead of doing it in .fb_destroy.

But ironically that change introduced yet another use-after-free since the
fb_info was still used after the free.

This should fix for good by freeing the fb_info at the end of the handler.

Fixes: d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather than .remove")

are these patches going through any CI before being applied? Maybe would
be a good idea to cc intel-gfx mailing list on these fixes to have Intel
CI to pick them up for some tests?

pushed to drm-misc-fixes where the previous patch was applied.

thanks
LUcas De Marchi

Hello Lucas,

On 5/7/22 18:20, Lucas De Marchi wrote:

On Fri, May 06, 2022 at 03:22:25PM +0200, Javier Martinez Canillas wrote:

quoted

Commit d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather
than .remove") attempted to fix a use-after-free error due driver freeing
the fb_info in the .remove handler instead of doing it in .fb_destroy.

But ironically that change introduced yet another use-after-free since the
fb_info was still used after the free.

This should fix for good by freeing the fb_info at the end of the handler.

Fixes: d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather than .remove")

are these patches going through any CI before being applied? Maybe would
be a good idea to cc intel-gfx mailing list on these fixes to have Intel
CI to pick them up for some tests?

I Cc'ed intel-gfx for this particular patch. I should had done it for the
previous patches too, but I wasn't aware that Cc'ing that list would make
it run on your CI.

I tested locally the offending patch on an EFI platform before applying it
and I don't know why it didn't fail there. Sorry all for the inconvenience.
 

pushed to drm-misc-fixes where the previous patch was applied.

Thanks.

-- 
Best regards,

Javier Martinez Canillas
Linux Engineering
Red Hat