Re: [PATCH v2] fbdev: Make fb_release() return -ENODEV if fbdev was unregistered

[Daniel Vetter]

On Tue, May 03, 2022 at 05:28:09PM +0200, Javier Martinez Canillas wrote:
> On 5/2/22 15:50, Javier Martinez Canillas wrote:
> > A reference to the framebuffer device struct fb_info is stored in the file
> > private data, but this reference could no longer be valid and must not be
> > accessed directly. Instead, the file_fb_info() accessor function must be
> > used since it does sanity checking to make sure that the fb_info is valid.
> > 
> > This can happen for example if the registered framebuffer device is for a
> > driver that just uses a framebuffer provided by the system firmware. In
> > that case, the fbdev core would unregister the framebuffer device when a
> > real video driver is probed and ask to remove conflicting framebuffers.
> > 
> > The bug has been present for a long time but commit 27599aacbaef ("fbdev:
> > Hot-unplug firmware fb devices on forced removal") unmasked it since the
> > fbdev core started unregistering the framebuffers' devices associated.
> > 
> > Fixes: 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal")
> > Reported-by: Maxime Ripard <maxime@xxxxxxxxxx>
> > Reported-by: Junxiao Chang <junxiao.chang@xxxxxxxxx>
> > Signed-off-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
> > Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> > ---
> Applied to drm-misc (drm-misc-fixes).

See my other reply, but how does this not result in leaks?
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch