From: Kevin Hao haokexin@gmail.com
[ Upstream commit 72139dfa2464e43957d330266994740bb7be2535 ]
The struct cdev is embedded in the struct watchdog_core_data. In the current code, we manage the watchdog_core_data with a kref, but the cdev is manged by a kobject. There is no any relationship between this kref and kobject. So it is possible that the watchdog_core_data is freed before the cdev is entirely released. We can easily get the following call trace with CONFIG_DEBUG_KOBJECT_RELEASE and CONFIG_DEBUG_OBJECTS_TIMERS enabled. ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x38 WARNING: CPU: 23 PID: 1028 at lib/debugobjects.c:481 debug_print_object+0xb0/0xf0 Modules linked in: softdog(-) deflate ctr twofish_generic twofish_common camellia_generic serpent_generic blowfish_generic blowfish_common cast5_generic cast_common cmac xcbc af_key sch_fq_codel openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 CPU: 23 PID: 1028 Comm: modprobe Not tainted 5.3.0-next-20190924-yoctodev-standard+ #180 Hardware name: Marvell OcteonTX CN96XX board (DT) pstate: 00400009 (nzcv daif +PAN -UAO) pc : debug_print_object+0xb0/0xf0 lr : debug_print_object+0xb0/0xf0 sp : ffff80001cbcfc70 x29: ffff80001cbcfc70 x28: ffff800010ea2128 x27: ffff800010bad000 x26: 0000000000000000 x25: ffff80001103c640 x24: ffff80001107b268 x23: ffff800010bad9e8 x22: ffff800010ea2128 x21: ffff000bc2c62af8 x20: ffff80001103c600 x19: ffff800010e867d8 x18: 0000000000000060 x17: 0000000000000000 x16: 0000000000000000 x15: ffff000bd7240470 x14: 6e6968207473696c x13: 5f72656d6974203a x12: 6570797420746365 x11: 6a626f2029302065 x10: 7461747320657669 x9 : 7463612820657669 x8 : 3378302f3078302b x7 : 0000000000001d7a x6 : ffff800010fd5889 x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000 x2 : ffff000bff948548 x1 : 276a1c9e1edc2300 x0 : 0000000000000000 Call trace: debug_print_object+0xb0/0xf0 debug_check_no_obj_freed+0x1e8/0x210 kfree+0x1b8/0x368 watchdog_cdev_unregister+0x88/0xc8 watchdog_dev_unregister+0x38/0x48 watchdog_unregister_device+0xa8/0x100 softdog_exit+0x18/0xfec4 [softdog] __arm64_sys_delete_module+0x174/0x200 el0_svc_handler+0xd0/0x1c8 el0_svc+0x8/0xc
This is a common issue when using cdev embedded in a struct. Fortunately, we already have a mechanism to solve this kind of issue. Please see commit 233ed09d7fda ("chardev: add helper function to register char devs with a struct device") for more detail.
In this patch, we choose to embed the struct device into the watchdog_core_data, and use the API provided by the commit 233ed09d7fda to make sure that the release of watchdog_core_data and cdev are in sequence.
Signed-off-by: Kevin Hao haokexin@gmail.com Reviewed-by: Guenter Roeck linux@roeck-us.net Link: https://lore.kernel.org/r/20191008112934.29669-1-haokexin@gmail.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 --- drivers/watchdog/watchdog_dev.c | 70 +++++++++++++++------------------ 1 file changed, 32 insertions(+), 38 deletions(-)
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c index d3acc0a7256ca..62483a99105c0 100644 --- a/drivers/watchdog/watchdog_dev.c +++ b/drivers/watchdog/watchdog_dev.c @@ -34,7 +34,6 @@ #include <linux/init.h> /* For __init/__exit/... */ #include <linux/hrtimer.h> /* For hrtimers */ #include <linux/kernel.h> /* For printk/panic/... */ -#include <linux/kref.h> /* For data references */ #include <linux/kthread.h> /* For kthread_work */ #include <linux/miscdevice.h> /* For handling misc devices */ #include <linux/module.h> /* For module stuff/... */ @@ -52,14 +51,14 @@
/* * struct watchdog_core_data - watchdog core internal data - * @kref: Reference count. + * @dev: The watchdog's internal device * @cdev: The watchdog's Character device. * @wdd: Pointer to watchdog device. * @lock: Lock for watchdog core. * @status: Watchdog core internal status bits. */ struct watchdog_core_data { - struct kref kref; + struct device dev; struct cdev cdev; struct watchdog_device *wdd; struct mutex lock; @@ -840,7 +839,7 @@ static int watchdog_open(struct inode *inode, struct file *file) file->private_data = wd_data;
if (!hw_running) - kref_get(&wd_data->kref); + get_device(&wd_data->dev);
/* * open_timeout only applies for the first open from @@ -861,11 +860,11 @@ out_clear: return err; }
-static void watchdog_core_data_release(struct kref *kref) +static void watchdog_core_data_release(struct device *dev) { struct watchdog_core_data *wd_data;
- wd_data = container_of(kref, struct watchdog_core_data, kref); + wd_data = container_of(dev, struct watchdog_core_data, dev);
kfree(wd_data); } @@ -925,7 +924,7 @@ done: */ if (!running) { module_put(wd_data->cdev.owner); - kref_put(&wd_data->kref, watchdog_core_data_release); + put_device(&wd_data->dev); } return 0; } @@ -944,17 +943,22 @@ static struct miscdevice watchdog_miscdev = { .fops = &watchdog_fops, };
+static struct class watchdog_class = { + .name = "watchdog", + .owner = THIS_MODULE, + .dev_groups = wdt_groups, +}; + /* * watchdog_cdev_register: register watchdog character device * @wdd: watchdog device - * @devno: character device number * * Register a watchdog character device including handling the legacy * /dev/watchdog node. /dev/watchdog is actually a miscdevice and * thus we set it up like that. */
-static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno) +static int watchdog_cdev_register(struct watchdog_device *wdd) { struct watchdog_core_data *wd_data; int err; @@ -962,7 +966,6 @@ static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno) wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL); if (!wd_data) return -ENOMEM; - kref_init(&wd_data->kref); mutex_init(&wd_data->lock);
wd_data->wdd = wdd; @@ -991,23 +994,33 @@ static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno) } }
+ device_initialize(&wd_data->dev); + wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id); + wd_data->dev.class = &watchdog_class; + wd_data->dev.parent = wdd->parent; + wd_data->dev.groups = wdd->groups; + wd_data->dev.release = watchdog_core_data_release; + dev_set_drvdata(&wd_data->dev, wdd); + dev_set_name(&wd_data->dev, "watchdog%d", wdd->id); + /* Fill in the data structures */ cdev_init(&wd_data->cdev, &watchdog_fops); - wd_data->cdev.owner = wdd->ops->owner;
/* Add the device */ - err = cdev_add(&wd_data->cdev, devno, 1); + err = cdev_device_add(&wd_data->cdev, &wd_data->dev); if (err) { pr_err("watchdog%d unable to add device %d:%d\n", wdd->id, MAJOR(watchdog_devt), wdd->id); if (wdd->id == 0) { misc_deregister(&watchdog_miscdev); old_wd_data = NULL; - kref_put(&wd_data->kref, watchdog_core_data_release); + put_device(&wd_data->dev); } 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); @@ -1018,7 +1031,7 @@ static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno) */ if (watchdog_hw_running(wdd)) { __module_get(wdd->ops->owner); - kref_get(&wd_data->kref); + get_device(&wd_data->dev); if (handle_boot_enabled) hrtimer_start(&wd_data->timer, 0, HRTIMER_MODE_REL_HARD); @@ -1042,7 +1055,7 @@ static void watchdog_cdev_unregister(struct watchdog_device *wdd) { struct watchdog_core_data *wd_data = wdd->wd_data;
- cdev_del(&wd_data->cdev); + cdev_device_del(&wd_data->cdev, &wd_data->dev); if (wdd->id == 0) { misc_deregister(&watchdog_miscdev); old_wd_data = NULL; @@ -1061,15 +1074,9 @@ static void watchdog_cdev_unregister(struct watchdog_device *wdd) hrtimer_cancel(&wd_data->timer); kthread_cancel_work_sync(&wd_data->work);
- kref_put(&wd_data->kref, watchdog_core_data_release); + put_device(&wd_data->dev); }
-static struct class watchdog_class = { - .name = "watchdog", - .owner = THIS_MODULE, - .dev_groups = wdt_groups, -}; - static int watchdog_reboot_notifier(struct notifier_block *nb, unsigned long code, void *data) { @@ -1100,27 +1107,14 @@ static int watchdog_reboot_notifier(struct notifier_block *nb,
int watchdog_dev_register(struct watchdog_device *wdd) { - struct device *dev; - dev_t devno; int ret;
- devno = MKDEV(MAJOR(watchdog_devt), wdd->id); - - ret = watchdog_cdev_register(wdd, devno); + ret = watchdog_cdev_register(wdd); if (ret) return ret;
- dev = device_create_with_groups(&watchdog_class, wdd->parent, - devno, wdd, wdd->groups, - "watchdog%d", wdd->id); - if (IS_ERR(dev)) { - watchdog_cdev_unregister(wdd); - return PTR_ERR(dev); - } - ret = watchdog_register_pretimeout(wdd); if (ret) { - device_destroy(&watchdog_class, devno); watchdog_cdev_unregister(wdd); return ret; } @@ -1128,7 +1122,8 @@ int watchdog_dev_register(struct watchdog_device *wdd) if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) { wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
- ret = devm_register_reboot_notifier(dev, &wdd->reboot_nb); + ret = devm_register_reboot_notifier(&wdd->wd_data->dev, + &wdd->reboot_nb); if (ret) { pr_err("watchdog%d: Cannot register reboot notifier (%d)\n", wdd->id, ret); @@ -1150,7 +1145,6 @@ int watchdog_dev_register(struct watchdog_device *wdd) void watchdog_dev_unregister(struct watchdog_device *wdd) { watchdog_unregister_pretimeout(wdd); - device_destroy(&watchdog_class, wdd->wd_data->cdev.dev); watchdog_cdev_unregister(wdd); }