[PATCH 1/2] rtc: st-lpc: fix possible race condition

[PATCH 1/2] rtc: st-lpc: fix possible race condition

[Alexandre Belloni]

The IRQ is requested before the struct rtc is allocated and registered, but
this struct is used in the IRQ handler. This may lead to a NULL pointer
dereference.

Switch to devm_rtc_allocate_device/rtc_register_device to allocate the rtc
before requesting the IRQ.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
---
 drivers/rtc/rtc-st-lpc.c | 24 +++++++++---------------
 1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/drivers/rtc/rtc-st-lpc.c b/drivers/rtc/rtc-st-lpc.c
index d5222667f892..2f1ef2c28740 100644
--- a/drivers/rtc/rtc-st-lpc.c
+++ b/drivers/rtc/rtc-st-lpc.c
@@ -212,6 +212,10 @@ static int st_rtc_probe(struct platform_device *pdev)
 	if (!rtc)
 		return -ENOMEM;
 
+	rtc->rtc_dev = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(rtc->rtc_dev))
+		return PTR_ERR(rtc->rtc_dev);
+
 	spin_lock_init(&rtc->lock);
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
@@ -253,26 +257,17 @@ static int st_rtc_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, rtc);
 
-	rtc->rtc_dev = rtc_device_register("st-lpc-rtc", &pdev->dev,
-					   &st_rtc_ops, THIS_MODULE);
-	if (IS_ERR(rtc->rtc_dev)) {
+	rtc->rtc_dev->ops = &st_rtc_ops;
+
+	ret = rtc_register_device(rtc->rtc_dev);
+	if (ret) {
 		clk_disable_unprepare(rtc->clk);
-		return PTR_ERR(rtc->rtc_dev);
+		return ret;
 	}
 
 	return 0;
 }
 
-static int st_rtc_remove(struct platform_device *pdev)
-{
-	struct st_rtc *rtc = platform_get_drvdata(pdev);
-
-	if (likely(rtc->rtc_dev))
-		rtc_device_unregister(rtc->rtc_dev);
-
-	return 0;
-}
-
 #ifdef CONFIG_PM_SLEEP
 static int st_rtc_suspend(struct device *dev)
 {
@@ -325,7 +320,6 @@ static struct platform_driver st_rtc_platform_driver = {
 		.of_match_table = st_rtc_match,
 	},
 	.probe = st_rtc_probe,
-	.remove = st_rtc_remove,
 };
 
 module_platform_driver(st_rtc_platform_driver);
-- 
2.17.0

[PATCH 2/2] rtc: st-lpc: add range

[Alexandre Belloni]

The RTC has a 64 bit counter.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
---
 drivers/rtc/rtc-st-lpc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/rtc/rtc-st-lpc.c b/drivers/rtc/rtc-st-lpc.c
index 2f1ef2c28740..df467ace397b 100644
--- a/drivers/rtc/rtc-st-lpc.c
+++ b/drivers/rtc/rtc-st-lpc.c
@@ -258,6 +258,7 @@ static int st_rtc_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, rtc);
 
 	rtc->rtc_dev->ops = &st_rtc_ops;
+	rtc->range_max = do_div(U64_MAX, rtc->clkrate);
 
 	ret = rtc_register_device(rtc->rtc_dev);
 	if (ret) {
-- 
2.17.0

Re: [PATCH 2/2] rtc: st-lpc: add range

[kbuild test robot]

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Hi Alexandre,

I love your patch! Yet something to improve:

[auto build test ERROR on abelloni/rtc-next]
[also build test ERROR on v4.17-rc6 next-20180517]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Alexandre-Belloni/rtc-st-lpc-fix-possible-race-condition/20180521-192317
base:   https://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux.git rtc-next
config: arm-multi_v7_defconfig (attached as .config)
compiler: arm-linux-gnueabi-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=arm 

All error/warnings (new ones prefixed by >>):

   drivers/rtc/rtc-st-lpc.c: In function 'st_rtc_probe':
>> drivers/rtc/rtc-st-lpc.c:261:5: error: 'struct st_rtc' has no member named 'range_max'
     rtc->range_max = do_div(U64_MAX, rtc->clkrate);
        ^~
   In file included from arch/arm/include/asm/div64.h:127:0,
                    from include/linux/kernel.h:173,
                    from include/linux/clk.h:16,
                    from drivers/rtc/rtc-st-lpc.c:17:
>> include/asm-generic/div64.h:226:7: error: lvalue required as left operand of assignment
      (n) >>= ilog2(__base);   \
          ^
>> drivers/rtc/rtc-st-lpc.c:261:19: note: in expansion of macro 'do_div'
     rtc->range_max = do_div(U64_MAX, rtc->clkrate);
                      ^~~~~~
>> include/asm-generic/div64.h:230:31: warning: large integer implicitly truncated to unsigned type [-Woverflow]
      uint32_t __res_lo, __n_lo = (n); \
                                  ^
>> drivers/rtc/rtc-st-lpc.c:261:19: note: in expansion of macro 'do_div'
     rtc->range_max = do_div(U64_MAX, rtc->clkrate);
                      ^~~~~~
   include/asm-generic/div64.h:231:7: error: lvalue required as left operand of assignment
      (n) = __div64_const32(n, __base); \
          ^
>> drivers/rtc/rtc-st-lpc.c:261:19: note: in expansion of macro 'do_div'
     rtc->range_max = do_div(U64_MAX, rtc->clkrate);
                      ^~~~~~
   include/asm-generic/div64.h:233:14: warning: large integer implicitly truncated to unsigned type [-Woverflow]
      __res_lo = (n);    \
                 ^
>> drivers/rtc/rtc-st-lpc.c:261:19: note: in expansion of macro 'do_div'
     rtc->range_max = do_div(U64_MAX, rtc->clkrate);
                      ^~~~~~
   include/asm-generic/div64.h:237:7: error: lvalue required as left operand of assignment
      (n) = (uint32_t)(n) / __base;  \
          ^
>> drivers/rtc/rtc-st-lpc.c:261:19: note: in expansion of macro 'do_div'
     rtc->range_max = do_div(U64_MAX, rtc->clkrate);
                      ^~~~~~
>> include/asm-generic/div64.h:239:22: error: lvalue required as unary '&' operand
      __rem = __div64_32(&(n), __base); \
                         ^
>> drivers/rtc/rtc-st-lpc.c:261:19: note: in expansion of macro 'do_div'
     rtc->range_max = do_div(U64_MAX, rtc->clkrate);
                      ^~~~~~
--
   drivers//rtc/rtc-st-lpc.c: In function 'st_rtc_probe':
   drivers//rtc/rtc-st-lpc.c:261:5: error: 'struct st_rtc' has no member named 'range_max'
     rtc->range_max = do_div(U64_MAX, rtc->clkrate);
        ^~
   In file included from arch/arm/include/asm/div64.h:127:0,
                    from include/linux/kernel.h:173,
                    from include/linux/clk.h:16,
                    from drivers//rtc/rtc-st-lpc.c:17:
>> include/asm-generic/div64.h:226:7: error: lvalue required as left operand of assignment
      (n) >>= ilog2(__base);   \
          ^
   drivers//rtc/rtc-st-lpc.c:261:19: note: in expansion of macro 'do_div'
     rtc->range_max = do_div(U64_MAX, rtc->clkrate);
                      ^~~~~~
>> include/asm-generic/div64.h:230:31: warning: large integer implicitly truncated to unsigned type [-Woverflow]
      uint32_t __res_lo, __n_lo = (n); \
                                  ^
   drivers//rtc/rtc-st-lpc.c:261:19: note: in expansion of macro 'do_div'
     rtc->range_max = do_div(U64_MAX, rtc->clkrate);
                      ^~~~~~
   include/asm-generic/div64.h:231:7: error: lvalue required as left operand of assignment
      (n) = __div64_const32(n, __base); \
          ^
   drivers//rtc/rtc-st-lpc.c:261:19: note: in expansion of macro 'do_div'
     rtc->range_max = do_div(U64_MAX, rtc->clkrate);
                      ^~~~~~
   include/asm-generic/div64.h:233:14: warning: large integer implicitly truncated to unsigned type [-Woverflow]
      __res_lo = (n);    \
                 ^
   drivers//rtc/rtc-st-lpc.c:261:19: note: in expansion of macro 'do_div'
     rtc->range_max = do_div(U64_MAX, rtc->clkrate);
                      ^~~~~~
   include/asm-generic/div64.h:237:7: error: lvalue required as left operand of assignment
      (n) = (uint32_t)(n) / __base;  \
          ^
   drivers//rtc/rtc-st-lpc.c:261:19: note: in expansion of macro 'do_div'
     rtc->range_max = do_div(U64_MAX, rtc->clkrate);
                      ^~~~~~
>> include/asm-generic/div64.h:239:22: error: lvalue required as unary '&' operand
      __rem = __div64_32(&(n), __base); \
                         ^
   drivers//rtc/rtc-st-lpc.c:261:19: note: in expansion of macro 'do_div'
     rtc->range_max = do_div(U64_MAX, rtc->clkrate);
                      ^~~~~~

vim +261 drivers/rtc/rtc-st-lpc.c

   192	
   193	static int st_rtc_probe(struct platform_device *pdev)
   194	{
   195		struct device_node *np = pdev->dev.of_node;
   196		struct st_rtc *rtc;
   197		struct resource *res;
   198		uint32_t mode;
   199		int ret = 0;
   200	
   201		ret = of_property_read_u32(np, "st,lpc-mode", &mode);
   202		if (ret) {
   203			dev_err(&pdev->dev, "An LPC mode must be provided\n");
   204			return -EINVAL;
   205		}
   206	
   207		/* LPC can either run as a Clocksource or in RTC or WDT mode */
   208		if (mode != ST_LPC_MODE_RTC)
   209			return -ENODEV;
   210	
   211		rtc = devm_kzalloc(&pdev->dev, sizeof(struct st_rtc), GFP_KERNEL);
   212		if (!rtc)
   213			return -ENOMEM;
   214	
   215		rtc->rtc_dev = devm_rtc_allocate_device(&pdev->dev);
   216		if (IS_ERR(rtc->rtc_dev))
   217			return PTR_ERR(rtc->rtc_dev);
   218	
   219		spin_lock_init(&rtc->lock);
   220	
   221		res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
   222		rtc->ioaddr = devm_ioremap_resource(&pdev->dev, res);
   223		if (IS_ERR(rtc->ioaddr))
   224			return PTR_ERR(rtc->ioaddr);
   225	
   226		rtc->irq = irq_of_parse_and_map(np, 0);
   227		if (!rtc->irq) {
   228			dev_err(&pdev->dev, "IRQ missing or invalid\n");
   229			return -EINVAL;
   230		}
   231	
   232		ret = devm_request_irq(&pdev->dev, rtc->irq, st_rtc_handler, 0,
   233				       pdev->name, rtc);
   234		if (ret) {
   235			dev_err(&pdev->dev, "Failed to request irq %i\n", rtc->irq);
   236			return ret;
   237		}
   238	
   239		enable_irq_wake(rtc->irq);
   240		disable_irq(rtc->irq);
   241	
   242		rtc->clk = clk_get(&pdev->dev, NULL);
   243		if (IS_ERR(rtc->clk)) {
   244			dev_err(&pdev->dev, "Unable to request clock\n");
   245			return PTR_ERR(rtc->clk);
   246		}
   247	
   248		clk_prepare_enable(rtc->clk);
   249	
   250		rtc->clkrate = clk_get_rate(rtc->clk);
   251		if (!rtc->clkrate) {
   252			dev_err(&pdev->dev, "Unable to fetch clock rate\n");
   253			return -EINVAL;
   254		}
   255	
   256		device_set_wakeup_capable(&pdev->dev, 1);
   257	
   258		platform_set_drvdata(pdev, rtc);
   259	
   260		rtc->rtc_dev->ops = &st_rtc_ops;
 > 261		rtc->range_max = do_div(U64_MAX, rtc->clkrate);
   262	
   263		ret = rtc_register_device(rtc->rtc_dev);
   264		if (ret) {
   265			clk_disable_unprepare(rtc->clk);
   266			return ret;
   267		}
   268	
   269		return 0;
   270	}
   271	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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Re: [PATCH 1/2] rtc: st-lpc: fix possible race condition

[Patrice CHOTARD]

Hi Alexandre

On 05/20/2018 02:33 PM, Alexandre Belloni wrote:
> The IRQ is requested before the struct rtc is allocated and registered, but
> this struct is used in the IRQ handler. This may lead to a NULL pointer
> dereference.
> 
> Switch to devm_rtc_allocate_device/rtc_register_device to allocate the rtc
> before requesting the IRQ.
> 
> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
> ---
>   drivers/rtc/rtc-st-lpc.c | 24 +++++++++---------------
>   1 file changed, 9 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-st-lpc.c b/drivers/rtc/rtc-st-lpc.c
> index d5222667f892..2f1ef2c28740 100644
> --- a/drivers/rtc/rtc-st-lpc.c
> +++ b/drivers/rtc/rtc-st-lpc.c
> @@ -212,6 +212,10 @@ static int st_rtc_probe(struct platform_device *pdev)
>   	if (!rtc)
>   		return -ENOMEM;
>   
> +	rtc->rtc_dev = devm_rtc_allocate_device(&pdev->dev);
> +	if (IS_ERR(rtc->rtc_dev))
> +		return PTR_ERR(rtc->rtc_dev);
> +
>   	spin_lock_init(&rtc->lock);
>   
>   	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> @@ -253,26 +257,17 @@ static int st_rtc_probe(struct platform_device *pdev)
>   
>   	platform_set_drvdata(pdev, rtc);
>   
> -	rtc->rtc_dev = rtc_device_register("st-lpc-rtc", &pdev->dev,
> -					   &st_rtc_ops, THIS_MODULE);
> -	if (IS_ERR(rtc->rtc_dev)) {
> +	rtc->rtc_dev->ops = &st_rtc_ops;
> +
> +	ret = rtc_register_device(rtc->rtc_dev);
> +	if (ret) {
>   		clk_disable_unprepare(rtc->clk);
> -		return PTR_ERR(rtc->rtc_dev);
> +		return ret;
>   	}
>   
>   	return 0;
>   }
>   
> -static int st_rtc_remove(struct platform_device *pdev)
> -{
> -	struct st_rtc *rtc = platform_get_drvdata(pdev);
> -
> -	if (likely(rtc->rtc_dev))
> -		rtc_device_unregister(rtc->rtc_dev);
> -
> -	return 0;
> -}
> -
>   #ifdef CONFIG_PM_SLEEP
>   static int st_rtc_suspend(struct device *dev)
>   {
> @@ -325,7 +320,6 @@ static struct platform_driver st_rtc_platform_driver = {
>   		.of_match_table = st_rtc_match,
>   	},
>   	.probe = st_rtc_probe,
> -	.remove = st_rtc_remove,
>   };
>   
>   module_platform_driver(st_rtc_platform_driver);
> 

Acked-by: Patrice Chotard <patrice.chotard@st.com>

Thanks

Patrice