This is a note to let you know that I've just added the patch titled
fbdev: Prevent possible use-after-free in fb_release()
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
fbdev-prevent-possible-use-after-free-in-fb_release.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 6482e9f6a97501252eac6bf4a54636431b05e80e
Author: Daniel Vetter <daniel.vetter@xxxxxxxx>
Date: Fri May 6 00:04:13 2022 +0200
fbdev: Prevent possible use-after-free in fb_release()
[ Upstream commit 89bfd4017e58faaf70411555e7f508495114e90b ]
Most fbdev drivers have issues with the fb_info lifetime, because call to
framebuffer_release() from their driver's .remove callback, rather than
doing from fbops.fb_destroy callback.
Doing that will destroy the fb_info too early, while references to it may
still exist, leading to a use-after-free error.
To prevent this, check the fb_info reference counter when attempting to
kfree the data structure in framebuffer_release(). That will leak it but
at least will prevent the mentioned error.
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Signed-off-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20220505220413.365977-1-javierm@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/video/fbdev/core/fbsysfs.c b/drivers/video/fbdev/core/fbsysfs.c
index 65dae05fff8e..ce699396d6ba 100644
--- a/drivers/video/fbdev/core/fbsysfs.c
+++ b/drivers/video/fbdev/core/fbsysfs.c
@@ -80,6 +80,10 @@ void framebuffer_release(struct fb_info *info)
{
if (!info)
return;
+
+ if (WARN_ON(refcount_read(&info->count)))
+ return;
+
kfree(info->apertures);
kfree(info);
}
