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(-)

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)