RE: [PATCH V2] rtc: snvs: fix possible race condition

[Anson Huang]

Hi, Alexandre

> On 19/07/2019 11:01:02+0800, anson.hu...@nxp.com wrote:
> > From: Anson Huang 
> >
> > The RTC IRQ is requested before the struct rtc_device is allocated,
> > this may lead to a NULL pointer dereference in IRQ handler.
> >
> > To fix this issue, allocating the rtc_device struct and register rtc
> > device before requesting the RTC IRQ.
> >
> > Using devm_rtc_allocate_device/rtc_register_device instead of
> > devm_rtc_device_register.
> >
> > Signed-off-by: Anson Huang 
> > ---
> > Changes since V1:
> > - move devm_request_irq() to after rtc device register done, make
> sure everything
> >   is ready before enabling IRQ.
> 
> This opens another race condition, the first version of the patch was correct.

Hmm, OK, then we should go with V1.

Thanks,
Anson.

Re: [PATCH V2] rtc: snvs: fix possible race condition

[Alexandre Belloni]

On 19/07/2019 11:01:02+0800, anson.hu...@nxp.com wrote:
> From: Anson Huang 
> 
> The RTC IRQ is requested before the struct rtc_device is allocated,
> this may lead to a NULL pointer dereference in IRQ handler.
> 
> To fix this issue, allocating the rtc_device struct and register rtc
> device before requesting the RTC IRQ.
> 
> Using devm_rtc_allocate_device/rtc_register_device instead of
> devm_rtc_device_register.
> 
> Signed-off-by: Anson Huang 
> ---
> Changes since V1:
>   - move devm_request_irq() to after rtc device register done, make sure 
> everything
> is ready before enabling IRQ.

This opens another race condition, the first version of the patch was
correct.

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

[PATCH V2] rtc: snvs: fix possible race condition

[Anson . Huang]

From: Anson Huang 

The RTC IRQ is requested before the struct rtc_device is allocated,
this may lead to a NULL pointer dereference in IRQ handler.

To fix this issue, allocating the rtc_device struct and register rtc
device before requesting the RTC IRQ.

Using devm_rtc_allocate_device/rtc_register_device instead of
devm_rtc_device_register.

Signed-off-by: Anson Huang 
---
Changes since V1:
- move devm_request_irq() to after rtc device register done, make sure 
everything
  is ready before enabling IRQ.
---
 drivers/rtc/rtc-snvs.c | 19 +++
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/rtc/rtc-snvs.c b/drivers/rtc/rtc-snvs.c
index 7ee673a2..d9650e7 100644
--- a/drivers/rtc/rtc-snvs.c
+++ b/drivers/rtc/rtc-snvs.c
@@ -279,6 +279,10 @@ static int snvs_rtc_probe(struct platform_device *pdev)
if (!data)
return -ENOMEM;
 
+   data->rtc = devm_rtc_allocate_device(>dev);
+   if (IS_ERR(data->rtc))
+   return PTR_ERR(data->rtc);
+
data->regmap = syscon_regmap_lookup_by_phandle(pdev->dev.of_node, 
"regmap");
 
if (IS_ERR(data->regmap)) {
@@ -335,6 +339,13 @@ static int snvs_rtc_probe(struct platform_device *pdev)
if (ret)
dev_err(>dev, "failed to enable irq wake\n");
 
+   data->rtc->ops = _rtc_ops;
+   ret = rtc_register_device(data->rtc);
+   if (ret) {
+   dev_err(>dev, "failed to register rtc: %d\n", ret);
+   goto error_rtc_device_register;
+   }
+
ret = devm_request_irq(>dev, data->irq, snvs_rtc_irq_handler,
   IRQF_SHARED, "rtc alarm", >dev);
if (ret) {
@@ -343,14 +354,6 @@ static int snvs_rtc_probe(struct platform_device *pdev)
goto error_rtc_device_register;
}
 
-   data->rtc = devm_rtc_device_register(>dev, pdev->name,
-   _rtc_ops, THIS_MODULE);
-   if (IS_ERR(data->rtc)) {
-   ret = PTR_ERR(data->rtc);
-   dev_err(>dev, "failed to register rtc: %d\n", ret);
-   goto error_rtc_device_register;
-   }
-
return 0;
 
 error_rtc_device_register:
-- 
2.7.4