| Message ID | 20220502135014.377945-1-javierm@redhat.com (mailing list archive) |
|---|---|
| State | Mainlined |
| Headers | show |
| Series | [v2] fbdev: Make fb_release() return -ENODEV if fbdev was unregistered | expand |
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@cerno.tech> > Reported-by: Junxiao Chang <junxiao.chang@intel.com> > Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> > Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de> > --- Applied to drm-misc (drm-misc-fixes).
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@cerno.tech> > > Reported-by: Junxiao Chang <junxiao.chang@intel.com> > > Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> > > Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de> > > --- > Applied to drm-misc (drm-misc-fixes). See my other reply, but how does this not result in leaks? -Daniel
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 84427470367b..82d4318ba8f7 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1434,7 +1434,10 @@ fb_release(struct inode *inode, struct file *file) __acquires(&info->lock) __releases(&info->lock) { - struct fb_info * const info = file->private_data; + struct fb_info * const info = file_fb_info(file); + + if (!info) + return -ENODEV; lock_fb_info(info); if (info->fbops->fb_release)
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@cerno.tech> Reported-by: Junxiao Chang <junxiao.chang@intel.com> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de> --- Changes in v2: - Drop patch 1/2 since patch 2/2 should be enough to fix the issue. - Add missing Fixes and Reported-by tags (Thomas Zimmermann). - Add Thomas Zimmermann's Reviewed-by tag. drivers/video/fbdev/core/fbmem.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)