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fbdev: Make fb_release() return -ENODEV if fbdev was unregistered

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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 27599aacba ("fbdev:
Hot-unplug firmware fb devices on forced removal") unmasked it since the
fbdev core started unregistering the framebuffers' devices associated.

Fixes: 27599aacba ("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-javierm@redhat.com
This commit is contained in:
Javier Martinez Canillas 2022-05-02 15:50:14 +02:00
parent dc3ae06c5f
commit aafa025c76
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1 changed files with 4 additions and 1 deletions
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5
drivers/video/fbdev/core/fbmem.c
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@ -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)