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

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Am 02.05.22 um 15:09 schrieb 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>

Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>

This seems like the correct thing to do in any case. Thanks for the patch. Before merging, you should also add

Fixes: 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal")
Reported-by: Junxiao Chang <junxiao.chang@xxxxxxxxx>

Best regards
Thomas

---

  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)

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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