From: Javier Martinez Canillas javierm@redhat.com

[ Upstream commit 135332f34ba2662bc1e32b5c612e06a8cc41a053 ]

This reverts commit aafa025c76dcc7d1a8c8f0bdefcbe4eb480b2f6a. That commit attempted to fix a NULL pointer dereference, caused by the struct fb_info associated with a framebuffer device to not longer be valid when the file descriptor was closed.

The issue was exposed by commit 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal"), which added a new path that goes through the struct device removal instead of directly unregistering the fb.

Most fbdev drivers have issues with the fb_info lifetime, because call to framebuffer_release() from their driver's .remove callback, rather than doing from fbops.fb_destroy callback. This meant that due to this switch, the fb_info was now destroyed too early, while references still existed, while before it was simply leaked.

The patch we're reverting here reinstated that leak, hence "fixed" the regression. But the proper solution is to fix the drivers to not release the fb_info too soon.

Suggested-by: Daniel Vetter daniel.vetter@ffwll.ch Signed-off-by: Javier Martinez Canillas javierm@redhat.com Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch Link: https://patchwork.freedesktop.org/patch/msgid/20220504115917.758787-1-javier... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/video/fbdev/core/fbmem.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 8e38a7a5cf2f..0371ad233fdf 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1436,10 +1436,7 @@ fb_release(struct inode *inode, struct file *file) __acquires(&info->lock) __releases(&info->lock) { - struct fb_info * const info = file_fb_info(file); - - if (!info) - return -ENODEV; + struct fb_info * const info = file->private_data;

lock_fb_info(info); if (info->fbops->fb_release)