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Subject[PATCH 1/2] rtc: tps6586x: fix possible race condition
Date
The probe function is not allowed to fail after the RTC is registered
because the following may happen:

CPU0: CPU1:
sys_load_module()
do_init_module()
do_one_initcall()
cmos_do_probe()
rtc_device_register()
__register_chrdev()
cdev->owner = struct module*
open("/dev/rtc0")
rtc_device_unregister()
module_put()
free_module()
module_free(mod->module_core)
/* struct module *module is now
freed */
chrdev_open()
spin_lock(cdev_lock)
cdev_get()
try_module_get()
module_is_live()
/* dereferences already
freed struct module* */

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
---
drivers/rtc/rtc-tps6586x.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/rtc/rtc-tps6586x.c b/drivers/rtc/rtc-tps6586x.c
index 46a19adf9a96..9b741143f131 100644
--- a/drivers/rtc/rtc-tps6586x.c
+++ b/drivers/rtc/rtc-tps6586x.c
@@ -276,14 +276,15 @@ static int tps6586x_rtc_probe(struct platform_device *pdev)
device_init_wakeup(&pdev->dev, 1);

platform_set_drvdata(pdev, rtc);
- rtc->rtc = devm_rtc_device_register(&pdev->dev, dev_name(&pdev->dev),
- &tps6586x_rtc_ops, THIS_MODULE);
+ rtc->rtc = devm_rtc_allocate_device(&pdev->dev);
if (IS_ERR(rtc->rtc)) {
ret = PTR_ERR(rtc->rtc);
- dev_err(&pdev->dev, "RTC device register: ret %d\n", ret);
+ dev_err(&pdev->dev, "RTC allocate device: ret %d\n", ret);
goto fail_rtc_register;
}

+ rtc->rtc->ops = &tps6586x_rtc_ops;
+
ret = devm_request_threaded_irq(&pdev->dev, rtc->irq, NULL,
tps6586x_rtc_irq,
IRQF_ONESHOT,
@@ -294,6 +295,13 @@ static int tps6586x_rtc_probe(struct platform_device *pdev)
goto fail_rtc_register;
}
disable_irq(rtc->irq);
+
+ ret = rtc_register_device(rtc->rtc);
+ if (ret) {
+ dev_err(&pdev->dev, "RTC device register: ret %d\n", ret);
+ goto fail_rtc_register;
+ }
+
return 0;

fail_rtc_register:
--
2.17.0
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