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

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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

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

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




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