[PATCH 1/3] mmc: sdhci-s3c: fix possible NULL pointer dereference when probed via platform

[PATCH 1/3] mmc: sdhci-s3c: fix possible NULL pointer dereference when probed via platform

[Krzysztof Kozlowski]

The driver can be matched by legacy platform way or OF-device matching.
In the first case, of_match_node() can return NULL, which immediately
would be dereferenced to get the match data.

Addresses-Coverity: Dereference null return value
Fixes: cd1b00eb24b0 ("mmc: sdhci-s3c: Add device tree support")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
---

Not tested on HW, but the code should be equivalent (plus safer).

 drivers/mmc/host/sdhci-s3c.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/mmc/host/sdhci-s3c.c b/drivers/mmc/host/sdhci-s3c.c
index f48a788a9d3d..8e1dca625620 100644
--- a/drivers/mmc/host/sdhci-s3c.c
+++ b/drivers/mmc/host/sdhci-s3c.c
@@ -20,6 +20,7 @@
 #include <linux/gpio.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/of_device.h>
 #include <linux/of_gpio.h>
 #include <linux/pm.h>
 #include <linux/pm_runtime.h>
@@ -461,19 +462,12 @@ static int sdhci_s3c_parse_dt(struct device *dev,
 }
 #endif
 
-#ifdef CONFIG_OF
-static const struct of_device_id sdhci_s3c_dt_match[];
-#endif
-
 static inline struct sdhci_s3c_drv_data *sdhci_s3c_get_driver_data(
 			struct platform_device *pdev)
 {
 #ifdef CONFIG_OF
-	if (pdev->dev.of_node) {
-		const struct of_device_id *match;
-		match = of_match_node(sdhci_s3c_dt_match, pdev->dev.of_node);
-		return (struct sdhci_s3c_drv_data *)match->data;
-	}
+	if (pdev->dev.of_node)
+		return (struct sdhci_s3c_drv_data *)of_device_get_match_data(&pdev->dev);
 #endif
 	return (struct sdhci_s3c_drv_data *)
 			platform_get_device_id(pdev)->driver_data;
-- 
2.25.1

[PATCH 2/3] mmc: sdhci-s3c: correct kerneldoc of sdhci_s3c_drv_data

[Krzysztof Kozlowski]

Correct the name of sdhci_s3c_drv_data structure in kerneldoc:

  drivers/mmc/host/sdhci-s3c.c:143: warning:
    expecting prototype for struct sdhci_s3c_driver_data. Prototype was for struct sdhci_s3c_drv_data instead

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
---
 drivers/mmc/host/sdhci-s3c.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-s3c.c b/drivers/mmc/host/sdhci-s3c.c
index 8e1dca625620..a07a8f011741 100644
--- a/drivers/mmc/host/sdhci-s3c.c
+++ b/drivers/mmc/host/sdhci-s3c.c
@@ -130,7 +130,7 @@ struct sdhci_s3c {
 };
 
 /**
- * struct sdhci_s3c_driver_data - S3C SDHCI platform specific driver data
+ * struct sdhci_s3c_drv_data - S3C SDHCI platform specific driver data
  * @sdhci_quirks: sdhci host specific quirks.
  * @no_divider: no or non-standard internal clock divider.
  *
-- 
2.25.1

[PATCH 3/3] mmc: sdhci-s3c: constify uses of driver/match data

[Krzysztof Kozlowski]

The driver data (struct sdhci_s3c_drv_data) stored in of_device_id
table is allocated as const and used only in const-way.  Skip
unnecessary const-away casts and convert all users to work with pointer
to const.  This is both more logical and safer.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
---
 drivers/mmc/host/sdhci-s3c.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/mmc/host/sdhci-s3c.c b/drivers/mmc/host/sdhci-s3c.c
index a07a8f011741..862f033d235d 100644
--- a/drivers/mmc/host/sdhci-s3c.c
+++ b/drivers/mmc/host/sdhci-s3c.c
@@ -462,21 +462,21 @@ static int sdhci_s3c_parse_dt(struct device *dev,
 }
 #endif
 
-static inline struct sdhci_s3c_drv_data *sdhci_s3c_get_driver_data(
+static inline const struct sdhci_s3c_drv_data *sdhci_s3c_get_driver_data(
 			struct platform_device *pdev)
 {
 #ifdef CONFIG_OF
 	if (pdev->dev.of_node)
-		return (struct sdhci_s3c_drv_data *)of_device_get_match_data(&pdev->dev);
+		return of_device_get_match_data(&pdev->dev);
 #endif
-	return (struct sdhci_s3c_drv_data *)
+	return (const struct sdhci_s3c_drv_data *)
 			platform_get_device_id(pdev)->driver_data;
 }
 
 static int sdhci_s3c_probe(struct platform_device *pdev)
 {
 	struct s3c_sdhci_platdata *pdata;
-	struct sdhci_s3c_drv_data *drv_data;
+	const struct sdhci_s3c_drv_data *drv_data;
 	struct device *dev = &pdev->dev;
 	struct sdhci_host *host;
 	struct sdhci_s3c *sc;
@@ -761,7 +761,7 @@ static const struct platform_device_id sdhci_s3c_driver_ids[] = {
 MODULE_DEVICE_TABLE(platform, sdhci_s3c_driver_ids);
 
 #ifdef CONFIG_OF
-static struct sdhci_s3c_drv_data exynos4_sdhci_drv_data = {
+static const struct sdhci_s3c_drv_data exynos4_sdhci_drv_data = {
 	.no_divider = true,
 };
 
-- 
2.25.1

Re: [PATCH 1/3] mmc: sdhci-s3c: fix possible NULL pointer dereference when probed via platform

[Krzysztof Kozlowski]

On 14/04/2021 17:12, Krzysztof Kozlowski wrote:
> The driver can be matched by legacy platform way or OF-device matching.
> In the first case, of_match_node() can return NULL, which immediately
> would be dereferenced to get the match data.
> 
> Addresses-Coverity: Dereference null return value
> Fixes: cd1b00eb24b0 ("mmc: sdhci-s3c: Add device tree support")
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
> ---
> 
> Not tested on HW, but the code should be equivalent (plus safer).
> 
>  drivers/mmc/host/sdhci-s3c.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-s3c.c b/drivers/mmc/host/sdhci-s3c.c
> index f48a788a9d3d..8e1dca625620 100644
> --- a/drivers/mmc/host/sdhci-s3c.c
> +++ b/drivers/mmc/host/sdhci-s3c.c
> @@ -20,6 +20,7 @@
>  #include <linux/gpio.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> +#include <linux/of_device.h>
>  #include <linux/of_gpio.h>
>  #include <linux/pm.h>
>  #include <linux/pm_runtime.h>
> @@ -461,19 +462,12 @@ static int sdhci_s3c_parse_dt(struct device *dev,
>  }
>  #endif
>  
> -#ifdef CONFIG_OF
> -static const struct of_device_id sdhci_s3c_dt_match[];
> -#endif
> -
>  static inline struct sdhci_s3c_drv_data *sdhci_s3c_get_driver_data(
>  			struct platform_device *pdev)
>  {
>  #ifdef CONFIG_OF
> -	if (pdev->dev.of_node) {
> -		const struct of_device_id *match;
> -		match = of_match_node(sdhci_s3c_dt_match, pdev->dev.of_node);

Now I have second thoughts whether NULL pointer can actually happen.  If
device is matched via platform/board files, maybe the pdev->dev.of_node
will be NULL thus skipping this branch?

Could there be a case where device is matched via platform_device_id()
(which has different name than compatible!) and (pdev->dev.of_node) is
still assigned? Maybe in case of out of tree DTS?

Anyway, the patch makes the code simpler/smaller, so I still think it is
reasonable. Just the severity of issue is questionable...

Best regards,
Krzysztof

Re: [PATCH 1/3] mmc: sdhci-s3c: fix possible NULL pointer dereference when probed via platform

[Sylwester Nawrocki]

On 14.04.2021 17:25, Krzysztof Kozlowski wrote:
> On 14/04/2021 17:12, Krzysztof Kozlowski wrote:
>> The driver can be matched by legacy platform way or OF-device matching.
>> In the first case, of_match_node() can return NULL, which immediately
>> would be dereferenced to get the match data.
>>
>> Addresses-Coverity: Dereference null return value
>> Fixes: cd1b00eb24b0 ("mmc: sdhci-s3c: Add device tree support")
>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>

>> -#ifdef CONFIG_OF
>> -static const struct of_device_id sdhci_s3c_dt_match[];
>> -#endif
>> -
>>   static inline struct sdhci_s3c_drv_data *sdhci_s3c_get_driver_data(
>>   			struct platform_device *pdev)
>>   {
>>   #ifdef CONFIG_OF
>> -	if (pdev->dev.of_node) {
>> -		const struct of_device_id *match;
>> -		match = of_match_node(sdhci_s3c_dt_match, pdev->dev.of_node);
> 
> Now I have second thoughts whether NULL pointer can actually happen.  If
> device is matched via platform/board files, maybe the pdev->dev.of_node
> will be NULL thus skipping this branch?
> 
> Could there be a case where device is matched via platform_device_id()
> (which has different name than compatible!) and (pdev->dev.of_node) is
> still assigned? Maybe in case of out of tree DTS?

That seems unlikely, the platform device would need to be initialized
via board file and then its of_node assigned somehow. It doesn't make
much sense to me. We either use board file or dtb to instantiate devices.

> Anyway, the patch makes the code simpler/smaller, so I still think it is
> reasonable. Just the severity of issue is questionable...

Yes, the patch looks good. Similar cleanups are already done in most of
the s3c/s5p/exynos drivers.

--
Thanks,
Sylwester

Re: [PATCH 1/3] mmc: sdhci-s3c: fix possible NULL pointer dereference when probed via platform

[Krzysztof Kozlowski]

On 14/04/2021 18:49, Sylwester Nawrocki wrote:
> On 14.04.2021 17:25, Krzysztof Kozlowski wrote:
>> On 14/04/2021 17:12, Krzysztof Kozlowski wrote:
>>> The driver can be matched by legacy platform way or OF-device matching.
>>> In the first case, of_match_node() can return NULL, which immediately
>>> would be dereferenced to get the match data.
>>>
>>> Addresses-Coverity: Dereference null return value
>>> Fixes: cd1b00eb24b0 ("mmc: sdhci-s3c: Add device tree support")
>>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
> 
>>> -#ifdef CONFIG_OF
>>> -static const struct of_device_id sdhci_s3c_dt_match[];
>>> -#endif
>>> -
>>>   static inline struct sdhci_s3c_drv_data *sdhci_s3c_get_driver_data(
>>>   			struct platform_device *pdev)
>>>   {
>>>   #ifdef CONFIG_OF
>>> -	if (pdev->dev.of_node) {
>>> -		const struct of_device_id *match;
>>> -		match = of_match_node(sdhci_s3c_dt_match, pdev->dev.of_node);
>>
>> Now I have second thoughts whether NULL pointer can actually happen.  If
>> device is matched via platform/board files, maybe the pdev->dev.of_node
>> will be NULL thus skipping this branch?
>>
>> Could there be a case where device is matched via platform_device_id()
>> (which has different name than compatible!) and (pdev->dev.of_node) is
>> still assigned? Maybe in case of out of tree DTS?
> 
> That seems unlikely, the platform device would need to be initialized
> via board file and then its of_node assigned somehow. It doesn't make
> much sense to me. We either use board file or dtb to instantiate devices.
> 
>> Anyway, the patch makes the code simpler/smaller, so I still think it is
>> reasonable. Just the severity of issue is questionable...
> 
> Yes, the patch looks good. Similar cleanups are already done in most of
> the s3c/s5p/exynos drivers.

Thanks Sylwester, I'll resend with different description.


Best regards,
Krzysztof