[PATCH 5.15 020/102] fbdev: efifb: Fix a use-after-free due early fb_info cleanup

Greg Kroah-Hartman
2022-05-16T19:54:15Z

From: Javier Martinez Canillas <javierm@redhat.com>

[ Upstream commit 1b5853dfab7fdde450f00f145327342238135c8a ]

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@linux.intel.com>
Reported-by: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Reviewed-by: Thomas Zimmermann <tzimemrmann@suse.de>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220506132225.588379-1-javierm@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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