From: Daniel Vetter daniel.vetter@ffwll.ch

[ 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@intel.com Signed-off-by: Javier Martinez Canillas javierm@redhat.com Reviewed-by: Thomas Zimmermann tzimmermann@suse.de Link: https://patchwork.freedesktop.org/patch/msgid/20220505220413.365977-1-javier... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/video/fbdev/core/fbsysfs.c | 4 ++++ 1 file changed, 4 insertions(+)

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); }