From 81d9367199e2a3490921d13cc8c54bde5f6ea44d Mon Sep 17 00:00:00 2001
From: Javier Martinez Canillas <javierm@redhat.com>
Date: Wed, 4 May 2022 13:59:17 +0200
Subject: Revert "fbdev: Make fb_release() return -ENODEV if fbdev was
unregistered"
Git-commit: 135332f34ba2662bc1e32b5c612e06a8cc41a053
Patch-mainline: v5.18-rc7
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225
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-javierm@redhat.com
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
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 97eb0dee411c..a6bb0e438216 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1434,10 +1434,7 @@ 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)
--
2.38.1