From: Kevin Hao haokexin@gmail.com
commit 1413ef638abae4ab5621901cf4d8ef08a4a48ba6 upstream.
The struct cdev is embedded in the struct i2c_dev. In the current code, we would free the i2c_dev struct directly in put_i2c_dev(), but the cdev is manged by a kobject, and the release of it is not predictable. So it is very possible that the i2c_dev 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: 19 PID: 1 at lib/debugobjects.c:325 debug_print_object+0xb0/0xf0 Modules linked in: CPU: 19 PID: 1 Comm: swapper/0 Tainted: G W 5.2.20-yocto-standard+ #120 Hardware name: Marvell OcteonTX CN96XX board (DT) pstate: 80c00089 (Nzcv daIf +PAN +UAO) pc : debug_print_object+0xb0/0xf0 lr : debug_print_object+0xb0/0xf0 sp : ffff00001292f7d0 x29: ffff00001292f7d0 x28: ffff800b82151788 x27: 0000000000000001 x26: ffff800b892c0000 x25: ffff0000124a2558 x24: 0000000000000000 x23: ffff00001107a1d8 x22: ffff0000116b5088 x21: ffff800bdc6afca8 x20: ffff000012471ae8 x19: ffff00001168f2c8 x18: 0000000000000010 x17: 00000000fd6f304b x16: 00000000ee79de43 x15: ffff800bc0e80568 x14: 79616c6564203a74 x13: 6e6968207473696c x12: 5f72656d6974203a x11: ffff0000113f0018 x10: 0000000000000000 x9 : 000000000000001f x8 : 0000000000000000 x7 : ffff0000101294cc x6 : 0000000000000000 x5 : 0000000000000000 x4 : 0000000000000001 x3 : 00000000ffffffff x2 : 0000000000000000 x1 : 387fc15c8ec0f200 x0 : 0000000000000000 Call trace: debug_print_object+0xb0/0xf0 __debug_check_no_obj_freed+0x19c/0x228 debug_check_no_obj_freed+0x1c/0x28 kfree+0x250/0x440 put_i2c_dev+0x68/0x78 i2cdev_detach_adapter+0x60/0xc8 i2cdev_notifier_call+0x3c/0x70 notifier_call_chain+0x8c/0xe8 blocking_notifier_call_chain+0x64/0x88 device_del+0x74/0x380 device_unregister+0x54/0x78 i2c_del_adapter+0x278/0x2d0 unittest_i2c_bus_remove+0x3c/0x80 platform_drv_remove+0x30/0x50 device_release_driver_internal+0xf4/0x1c0 driver_detach+0x58/0xa0 bus_remove_driver+0x84/0xd8 driver_unregister+0x34/0x60 platform_driver_unregister+0x20/0x30 of_unittest_overlay+0x8d4/0xbe0 of_unittest+0xae8/0xb3c do_one_initcall+0xac/0x450 do_initcall_level+0x208/0x224 kernel_init_freeable+0x2d8/0x36c kernel_init+0x18/0x108 ret_from_fork+0x10/0x1c irq event stamp: 3934661 hardirqs last enabled at (3934661): [<ffff00001009fa04>] debug_exception_exit+0x4c/0x58 hardirqs last disabled at (3934660): [<ffff00001009fb14>] debug_exception_enter+0xa4/0xe0 softirqs last enabled at (3934654): [<ffff000010081d94>] __do_softirq+0x46c/0x628 softirqs last disabled at (3934649): [<ffff0000100b4a1c>] irq_exit+0x104/0x118
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 i2c_dev, and use the API provided by the commit 233ed09d7fda to make sure that the release of i2c_dev and cdev are in sequence.
Signed-off-by: Kevin Hao haokexin@gmail.com Signed-off-by: Wolfram Sang wsa@the-dreams.de Cc: Ben Hutchings ben.hutchings@codethink.co.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/i2c/i2c-dev.c | 48 ++++++++++++++++++++++++++---------------------- 1 file changed, 26 insertions(+), 22 deletions(-)
--- a/drivers/i2c/i2c-dev.c +++ b/drivers/i2c/i2c-dev.c @@ -40,7 +40,7 @@ struct i2c_dev { struct list_head list; struct i2c_adapter *adap; - struct device *dev; + struct device dev; struct cdev cdev; };
@@ -84,12 +84,14 @@ static struct i2c_dev *get_free_i2c_dev( return i2c_dev; }
-static void put_i2c_dev(struct i2c_dev *i2c_dev) +static void put_i2c_dev(struct i2c_dev *i2c_dev, bool del_cdev) { spin_lock(&i2c_dev_list_lock); list_del(&i2c_dev->list); spin_unlock(&i2c_dev_list_lock); - kfree(i2c_dev); + if (del_cdev) + cdev_device_del(&i2c_dev->cdev, &i2c_dev->dev); + put_device(&i2c_dev->dev); }
static ssize_t name_show(struct device *dev, @@ -628,6 +630,14 @@ static const struct file_operations i2cd
static struct class *i2c_dev_class;
+static void i2cdev_dev_release(struct device *dev) +{ + struct i2c_dev *i2c_dev; + + i2c_dev = container_of(dev, struct i2c_dev, dev); + kfree(i2c_dev); +} + static int i2cdev_attach_adapter(struct device *dev, void *dummy) { struct i2c_adapter *adap; @@ -644,27 +654,23 @@ static int i2cdev_attach_adapter(struct
cdev_init(&i2c_dev->cdev, &i2cdev_fops); i2c_dev->cdev.owner = THIS_MODULE; - res = cdev_add(&i2c_dev->cdev, MKDEV(I2C_MAJOR, adap->nr), 1); - if (res) - goto error_cdev; - - /* register this i2c device with the driver core */ - i2c_dev->dev = device_create(i2c_dev_class, &adap->dev, - MKDEV(I2C_MAJOR, adap->nr), NULL, - "i2c-%d", adap->nr); - if (IS_ERR(i2c_dev->dev)) { - res = PTR_ERR(i2c_dev->dev); - goto error; + + device_initialize(&i2c_dev->dev); + i2c_dev->dev.devt = MKDEV(I2C_MAJOR, adap->nr); + i2c_dev->dev.class = i2c_dev_class; + i2c_dev->dev.parent = &adap->dev; + i2c_dev->dev.release = i2cdev_dev_release; + dev_set_name(&i2c_dev->dev, "i2c-%d", adap->nr); + + res = cdev_device_add(&i2c_dev->cdev, &i2c_dev->dev); + if (res) { + put_i2c_dev(i2c_dev, false); + return res; }
pr_debug("i2c-dev: adapter [%s] registered as minor %d\n", adap->name, adap->nr); return 0; -error: - cdev_del(&i2c_dev->cdev); -error_cdev: - put_i2c_dev(i2c_dev); - return res; }
static int i2cdev_detach_adapter(struct device *dev, void *dummy) @@ -680,9 +686,7 @@ static int i2cdev_detach_adapter(struct if (!i2c_dev) /* attach_adapter must have failed */ return 0;
- cdev_del(&i2c_dev->cdev); - put_i2c_dev(i2c_dev); - device_destroy(i2c_dev_class, MKDEV(I2C_MAJOR, adap->nr)); + put_i2c_dev(i2c_dev, true);
pr_debug("i2c-dev: adapter [%s] unregistered\n", adap->name); return 0;