This is a note to let you know that I've just added the patch titled
Revert "fbdev: Make fb_release() return -ENODEV if fbdev was unregistered"
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
revert-fbdev-make-fb_release-return-enodev-if-fbdev-.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 520380c39bd75da5178b67d7e5f8cd682e5a81cb
Author: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Date: Wed May 4 13:59:17 2022 +0200
Revert "fbdev: Make fb_release() return -ENODEV if fbdev was unregistered"
[ 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@xxxxxxxx>
Signed-off-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20220504115917.758787-1-javierm@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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)
