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gpiolib: Fix return value of gpio_to_desc() stub if !GPIOLIB

PATCH In review Krzysztof Kozlowski 2 participants 4 messages Dec 6, 2018 – Dec 14, 2018

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Krzysztof Kozlowski

author
#0 lore raw

PATCH 1/1 gpiolib: Fix return value of gpio_to_desc() stub if !GPIOLIB

If CONFIG_GPOILIB is not set, the stub of gpio_to_desc() should return the same type of error as regular version: NULL. All the callers compare the return value of gpio_to_desc() against NULL, so returned ERR_PTR would be treated as non-error case leading to dereferencing of error value.

Fixes 79a9becda894 ("gpiolib: export descriptor-based GPIO interface")
Cc <[email protected]>
Signed-off-by Krzysztof Kozlowski <[email protected]>
---
 include/linux/gpio/consumer.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
include/linux/gpio/consumer.h +1 -1
index ed070512b40e..3b01fbcafc94 100644
@@ -505,7 +505,7 @@ static inline int gpiod_set_consumer_name(struct gpio_desc *desc,
 
 static inline struct gpio_desc *gpio_to_desc(unsigned gpio)
 {
-	return ERR_PTR(-EINVAL);
+	return NULL;
 }
 
 static inline int desc_to_gpio(const struct gpio_desc *desc)
Signature · 1 line
2.7.4
#1 lore raw
Quoted 18 lines · Krzysztof Kozlowski

If CONFIG_GPOILIB is not set, the stub of gpio_to_desc() should return the same type of error as regular version: NULL. All the callers compare the return value of gpio_to_desc() against NULL, so returned ERR_PTR would be treated as non-error case leading to dereferencing of error value.

Fixes 79a9becda894 ("gpiolib: export descriptor-based GPIO interface")
Cc <[email protected]>
Signed-off-by Krzysztof Kozlowski <[email protected]>
---
 include/linux/gpio/consumer.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
include/linux/gpio/consumer.h +0 -0
index ed070512b40e..3b01fbcafc94 100644

include/linux/gpio/consumer.h static inline int gpiod_set_consumer_name(struct gpio_desc *desc, · line 508

Quoted 5 lines
include/linux/gpio/consumer.h +1 -1
@@ -505,7 +505,7 @@ static inline int gpiod_set_consumer_name(struct gpio_desc *desc,
 
 static inline struct gpio_desc *gpio_to_desc(unsigned gpio)
 {
-       return ERR_PTR(-EINVAL);
+       return NULL;

I suppose this is consistent with comitt:
22c403676dbbb7c6f186099527af7f065498ef45
"gpio: return NULL from gpiod_get_optional when GPIOLIB is disabled"

So in that way it should be fine.

I'm just wondering where you see this problem, because IMO a driver that is using GPIO should either
depends on GPIOLIB or
select GPIOLIB
it is extremely uncommon for a GPIO line to actually be optional at compile time (as opposed to optional at runtime) so I would very much like to look closer at this.

Yours,
Linus Walleij

author
#2 lore raw
Quoted 33 lines · Linus Walleij
Quoted 18 lines · Krzysztof Kozlowski

If CONFIG_GPOILIB is not set, the stub of gpio_to_desc() should return the same type of error as regular version: NULL. All the callers compare the return value of gpio_to_desc() against NULL, so returned ERR_PTR would be treated as non-error case leading to dereferencing of error value.

Fixes 79a9becda894 ("gpiolib: export descriptor-based GPIO interface")
Cc <[email protected]>
Signed-off-by Krzysztof Kozlowski <[email protected]>
---
 include/linux/gpio/consumer.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
include/linux/gpio/consumer.h +0 -0
index ed070512b40e..3b01fbcafc94 100644

include/linux/gpio/consumer.h static inline int gpiod_set_consumer_name(struct gpio_desc *desc, · line 508

Quoted 5 lines
include/linux/gpio/consumer.h +1 -1
@@ -505,7 +505,7 @@ static inline int gpiod_set_consumer_name(struct gpio_desc *desc,
 
 static inline struct gpio_desc *gpio_to_desc(unsigned gpio)
 {
-       return ERR_PTR(-EINVAL);
+       return NULL;

I suppose this is consistent with comitt:
22c403676dbbb7c6f186099527af7f065498ef45
"gpio: return NULL from gpiod_get_optional when GPIOLIB is disabled"

So in that way it should be fine.

Quoted 7 lines

I'm just wondering where you see this problem, because IMO a driver that is using GPIO should either
depends on GPIOLIB or
select GPIOLIB
it is extremely uncommon for a GPIO line to actually be optional at compile time (as opposed to optional at runtime) so I would very much like to look closer at this.

No, I did not hit this error. Maybe I should mention this explicitly that this case is rather theoretical (feel free to change the commit msg respectively). What is however important, it misleads developers which test for ERR_PTR, like before this fix:
2d88a331e48095cf60ad9bdf3177bd401bf99727 ("leds: leds-gpio: Fix return value check in create_gpio_led()")

Best regards,
Krzysztof

#3 lore raw
In reply to Krzysztof Kozlowski
Quoted 9 lines · Krzysztof Kozlowski

If CONFIG_GPOILIB is not set, the stub of gpio_to_desc() should return the same type of error as regular version: NULL. All the callers compare the return value of gpio_to_desc() against NULL, so returned ERR_PTR would be treated as non-error case leading to dereferencing of error value.

Fixes 79a9becda894 ("gpiolib: export descriptor-based GPIO interface")
Cc <[email protected]>
Signed-off-by Krzysztof Kozlowski <[email protected]>

Patch applied. I kept the Fixes but removed stable, I do not know of any regression it is fixing.

Yours,
Linus Walleij