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fbdev: Use device_create_with_groups() to fix sysfs groups registration race 

The fbdev sysfs attributes are registered after sending the uevent for
the device creation, leaving a race window where e.g. udev rules may
not be able to access the sysfs attributes because the registration is
not done yet.

Fix this by switching to device_create_with_groups(). This also results in
a nice cleanup. After switching to device_create_with_groups() all that
is left of fb_init_device() is setting the drvdata and that can be passed
to device_create[_with_groups]() too. After which fb_init_device() can
be completely removed.

Dropping fb_init_device() + fb_cleanup_device() in turn allows removing
fb_info.class_flag as they were the only user of this field.

Fixes: 5fc830d6ac ("fbdev: Register sysfs groups through device_add_group")
Cc: stable@vger.kernel.org
Cc: Shixiong Ou <oushixiong@kylinos.cn>
Signed-off-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Signed-off-by: Helge Deller <deller@gmx.de>
This commit is contained in:
Hans de Goede 2025-12-21 17:57:40 +01:00 committed by Helge Deller
parent 120adae7b4
commit 68eeb0871e
2 changed files with 3 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
drivers/video/fbdev/core/fbsysfs.c
View File

@ -12,8 +12,6 @@
#include "fb_internal.h"
#define FB_SYSFS_FLAG_ATTR 1
static int activate(struct fb_info *fb_info, struct fb_var_screeninfo *var)
{
int err;
@ -451,33 +449,7 @@ static struct attribute *fb_device_attrs[] = {
NULL,
};
static const struct attribute_group fb_device_attr_group = {
.attrs = fb_device_attrs,
};
static int fb_init_device(struct fb_info *fb_info)
{
int ret;
dev_set_drvdata(fb_info->dev, fb_info);
fb_info->class_flag |= FB_SYSFS_FLAG_ATTR;
ret = device_add_group(fb_info->dev, &fb_device_attr_group);
if (ret)
fb_info->class_flag &= ~FB_SYSFS_FLAG_ATTR;
return 0;
}
static void fb_cleanup_device(struct fb_info *fb_info)
{
if (fb_info->class_flag & FB_SYSFS_FLAG_ATTR) {
device_remove_group(fb_info->dev, &fb_device_attr_group);
fb_info->class_flag &= ~FB_SYSFS_FLAG_ATTR;
}
}
ATTRIBUTE_GROUPS(fb_device);
int fb_device_create(struct fb_info *fb_info)
{
@ -485,14 +457,13 @@ int fb_device_create(struct fb_info *fb_info)
dev_t devt = MKDEV(FB_MAJOR, node);
int ret;
fb_info->dev = device_create(fb_class, fb_info->device, devt, NULL, "fb%d", node);
fb_info->dev = device_create_with_groups(fb_class, fb_info->device, devt, fb_info,
fb_device_groups, "fb%d", node);
if (IS_ERR(fb_info->dev)) {
/* Not fatal */
ret = PTR_ERR(fb_info->dev);
pr_warn("Unable to create device for framebuffer %d; error %d\n", node, ret);
fb_info->dev = NULL;
} else {
fb_init_device(fb_info);
}
return 0;
@ -505,7 +476,6 @@ void fb_device_destroy(struct fb_info *fb_info)
if (!fb_info->dev)
return;
fb_cleanup_device(fb_info);
device_destroy(fb_class, devt);
fb_info->dev = NULL;
}

1
include/linux/fb.h
View File

@ -493,7 +493,6 @@ struct fb_info {
#if defined(CONFIG_FB_DEVICE)
struct device *dev; /* This is this fb device */
#endif
int class_flag; /* private sysfs flags */
#ifdef CONFIG_FB_TILEBLITTING
struct fb_tile_ops *tileops; /* Tile Blitting */
#endif