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rtc: class: don't call cdev_device_del() when cdev_device_add() failed

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I got a null-ptr-deref report when doing fault injection test:

general protection fault, probably for non-canonical address 0xdffffc0000000022: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000110-0x0000000000000117]
RIP: 0010:device_del+0x132/0xdc0
Call Trace:
 cdev_device_del+0x1a/0x80
 devm_rtc_unregister_device+0x37/0x80
 release_nodes+0xc3/0x3b0

If cdev_device_add() fails, 'dev->p' is not set, it causes
null-ptr-deref when calling cdev_device_del(). Registering
character device is optional, we don't return error code
here, so introduce a new flag 'RTC_NO_CDEV' to indicate
if it has character device, cdev_device_del() is called
when this bit is not set.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20211011132114.3663509-1-yangyingliang@huawei.com
This commit is contained in:
Yang Yingliang 2021-10-11 21:21:14 +08:00 committed by Alexandre Belloni
parent 7caadcfa8a
commit 789c1093f0
2 changed files with 7 additions and 3 deletions
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9
drivers/rtc/class.c
View file

@ -334,7 +334,8 @@ static void devm_rtc_unregister_device(void *data)
* letting any rtc_class_open() users access it again
*/
rtc_proc_del_device(rtc);
cdev_device_del(&rtc->char_dev, &rtc->dev);
if (!test_bit(RTC_NO_CDEV, &rtc->flags))
cdev_device_del(&rtc->char_dev, &rtc->dev);
rtc->ops = NULL;
mutex_unlock(&rtc->ops_lock);
}
@ -397,12 +398,14 @@ int __devm_rtc_register_device(struct module *owner, struct rtc_device *rtc)
rtc_dev_prepare(rtc);
err = cdev_device_add(&rtc->char_dev, &rtc->dev);
if (err)
if (err) {
set_bit(RTC_NO_CDEV, &rtc->flags);
dev_warn(rtc->dev.parent, "failed to add char device %d:%d\n",
MAJOR(rtc->dev.devt), rtc->id);
else
} else {
dev_dbg(rtc->dev.parent, "char device (%d:%d)\n",
MAJOR(rtc->dev.devt), rtc->id);
}
rtc_proc_add_device(rtc);

1
include/linux/rtc.h
View file

@ -80,6 +80,7 @@ struct rtc_timer {
/* flags */
#define RTC_DEV_BUSY 0
#define RTC_NO_CDEV 1
struct rtc_device {
struct device dev;