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

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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 <ville.syrjala@xxxxxxxxxxxxxxx>
Reported-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>
Signed-off-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>

Reviewed-by: Thomas Zimmermann <tzimemrmann@xxxxxxx>

---

  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 = {

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

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