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gpiolib: fix reference leaks when removing GPIO chips still in use

PATCH Superseded Bartosz Golaszewski 3 participants 4 messages Aug 10, 2023 GPIO

v1 of 3 Superseded Latest is v3 →

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Bartosz Golaszewski

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#0 lore raw

PATCH 1/1 gpiolib: fix reference leaks when removing GPIO chips still in use

From: Bartosz Golaszewski <[email protected]>

After we remove a GPIO chip that still has some requested descriptors, gpiod_free_commit() will fail and we will never put the references to the GPIO device and the owning module in gpiod_free().

Rework this function to:
- not warn on desc == NULL as this is a use-case on which most free functions silently return
- put the references to desc->gdev and desc->gdev->owner unconditionally so that the release callback actually gets called when the remaining references are dropped by external GPIO users

Signed-off-by Bartosz Golaszewski <[email protected]>

---
I'm going through the resource management issues one-by-one using the new virtual consumer module. This is something I found when I noticed that IDA numbers never get freed for a chip that was removed with descs still in use.

 drivers/gpio/gpiolib.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)
drivers/gpio/gpiolib.c +7 -5
index 251c875b5c34..7408e2561b2d 100644
@@ -2167,12 +2167,14 @@ static bool gpiod_free_commit(struct gpio_desc *desc)
 
 void gpiod_free(struct gpio_desc *desc)
 {
-	if (desc && desc->gdev && gpiod_free_commit(desc)) {
-		module_put(desc->gdev->owner);
-		gpio_device_put(desc->gdev);
-	} else {
+	if (!desc)
+		return;
+
+	if (!gpiod_free_commit(desc))
 		WARN_ON(extra_checks);
-	}
+
+	gpio_device_put(desc->gdev);
+	module_put(desc->gdev->owner);
 }
 
 /**
Signature · 1 line
2.39.2
Reviewed-by on v1 1/1
#1 lore raw
Quoted 6 lines · Bartosz Golaszewski

From: Bartosz Golaszewski <[email protected]>

After we remove a GPIO chip that still has some requested descriptors, gpiod_free_commit() will fail and we will never put the references to the GPIO device and the owning module in gpiod_free().

Quoted 8 lines

Rework this function to:
- not warn on desc == NULL as this is a use-case on which most free functions silently return
- put the references to desc->gdev and desc->gdev->owner unconditionally so that the release callback actually gets called when the remaining references are dropped by external GPIO users

Signed-off-by Bartosz Golaszewski <[email protected]>

Looks good to me!

Reviewed-by Linus Walleij <[email protected]>

Yours,
Linus Walleij

#2 lore raw
In reply to Bartosz Golaszewski
Quoted 12 lines · Bartosz Golaszewski

From: Bartosz Golaszewski <[email protected]>

After we remove a GPIO chip that still has some requested descriptors, gpiod_free_commit() will fail and we will never put the references to the GPIO device and the owning module in gpiod_free().

Rework this function to:
- not warn on desc == NULL as this is a use-case on which most free functions silently return
- put the references to desc->gdev and desc->gdev->owner unconditionally so that the release callback actually gets called when the remaining references are dropped by external GPIO users

...

drivers/gpio/gpiolib.c static bool gpiod_free_commit(struct gpio_desc *desc) · line 2171

Quoted 8 lines

void gpiod_free(struct gpio_desc *desc)
{

drivers/gpio/gpiolib.c +2 -4
-	if (desc && desc->gdev && gpiod_free_commit(desc)) {
-		module_put(desc->gdev->owner);
-		gpio_device_put(desc->gdev);
-	} else {
+	if (!desc)
+		return;

VALIDATE_DESC_VOID() ?

Quoted 7 lines
drivers/gpio/gpiolib.c +4 -1
+	if (!gpiod_free_commit(desc))
 		WARN_ON(extra_checks);
-	}
+
+	gpio_device_put(desc->gdev);
+	module_put(desc->gdev->owner);
 }
Signature · 2 lines
With Best Regards,
Andy Shevchenko
#3 lore raw
Quoted 2 lines · Andy Shevchenko
Quoted 1 line · Bartosz Golaszewski

From: Bartosz Golaszewski <[email protected]>

...

Quoted 10 lines

drivers/gpio/gpiolib.c static bool gpiod_free_commit(struct gpio_desc *desc) · line 2171

Quoted 8 lines

void gpiod_free(struct gpio_desc *desc)
{

drivers/gpio/gpiolib.c +2 -4
-	if (desc && desc->gdev && gpiod_free_commit(desc)) {
-		module_put(desc->gdev->owner);
-		gpio_device_put(desc->gdev);
-	} else {
+	if (!desc)
+		return;

VALIDATE_DESC_VOID() ?

If it is not possible to use, the comment should be added, like we have in gpiod_to_irq().

Quoted 7 lines
Quoted 7 lines
drivers/gpio/gpiolib.c +4 -1
+	if (!gpiod_free_commit(desc))
 		WARN_ON(extra_checks);
-	}
+
+	gpio_device_put(desc->gdev);
+	module_put(desc->gdev->owner);
 }
Signature · 2 lines
With Best Regards,
Andy Shevchenko