From: Javier Martinez Canillas javierm@redhat.com
[ Upstream commit aafa025c76dcc7d1a8c8f0bdefcbe4eb480b2f6a ]
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 Link: https://patchwork.freedesktop.org/patch/msgid/20220502135014.377945-1-javier... Signed-off-by: Sasha Levin sashal@kernel.org --- 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 00f0f282e7a1..10a9369c9dea 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1438,7 +1438,10 @@ 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)