mirrors
/
anolis-cloud-kernel
mirror of https://gitee.com/anolis/cloud-kernel.git
8
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

watchdog: set cdev owner before adding 

ANBZ: #9777

commit cbc15095d1ff2075a6a07cd7b783d4d5d5238118 5.10_lts.

[ Upstream commit 38d7529774 ]

When the new watchdog character device is registered, it becomes
available for opening. This creates a race where userspace may open the
device before the character device's owner is set. This results in an
imbalance in module_get calls as the cdev_get in cdev_open will not
increment the reference count on the watchdog driver module.

This causes problems when the watchdog character device is released as
the module loader's reference will also be released. This makes it
impossible to open the watchdog device later on as it now appears that
the module is being unloaded. The open will fail with -ENXIO from
chrdev_open.

The legacy watchdog device will fail with -EBUSY from the try_module_get
in watchdog_open because it's module owner is the watchdog core module
so it can still be opened but it will fail to get a refcount on the
underlying watchdog device driver.

Fixes: 72139dfa24 ("watchdog: Fix the race between the release of watchdog_core_data and cdev")
Signed-off-by: Curtis Klein <curtis.klein@hpe.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20231205190522.55153-1-curtis.klein@hpe.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Link: https://gitee.com/anolis/cloud-kernel/pulls/3719
This commit is contained in:
Curtis Klein 2023-12-05 11:05:22 -08:00 committed by 小龙
parent e37947e5f5
commit 5165c0cb8d
1 changed files with 1 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
drivers/watchdog/watchdog_dev.c
View File

@ -1028,6 +1028,7 @@ static int watchdog_cdev_register(struct watchdog_device *wdd)
/* Fill in the data structures */
cdev_init(&wd_data->cdev, &watchdog_fops);
wd_data->cdev.owner = wdd->ops->owner;
/* Add the device */
err = cdev_device_add(&wd_data->cdev, &wd_data->dev);
@ -1042,8 +1043,6 @@ static int watchdog_cdev_register(struct watchdog_device *wdd)
return err;
}
wd_data->cdev.owner = wdd->ops->owner;
/* Record time of most recent heartbeat as 'just before now'. */
wd_data->last_hw_keepalive = ktime_sub(ktime_get(), 1);
watchdog_set_open_deadline(wd_data);