[PATCH 2/2] fbdev: Make fb_release() return -ENODEV if fbdev was unregistered

[Javier Martinez Canillas]

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 fbdev driver was one that is using a
framebuffer provided by the system firmware. In that case, the fbdev core
could unregister the framebuffer device if a real video driver is probed.

Reported-by: Maxime Ripard <maxime@xxxxxxxxxx>
Signed-off-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
---

 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 20d8929df79f..d68097105f93 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1439,7 +1439,10 @@ 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)
-- 
2.35.1