[PATCH v4 2/7] gpiolib: free the label of lines released after their chip was removed

[Adrian Ambrozewicz <aambrozewicz@nvidia.com>]

gpiod_free_commit() drops the consumer label only while the chip is
still there. A line that user space keeps requested across
gpiochip_remove() is released when gdev->chip is already NULL, and its
label leaks:

  unreferenced object (size 32):
    comm "gpio-hold"
    backtrace (crc 7ff222d9):
      desc_set_label
      gpiod_request_commit
      gpiod_request
      linereq_create
      gpio_ioctl

Clear the label before the chip check. The ->free() callback, the flags
update and the line state notification need the chip and stay under it.

Reproduced with gpio-sim: request a line, set the chip's "live"
attribute to 0, then close the request. kmemleak reports up to 30 such
objects after 30 cycles; with this change, none after 100.

Fixes: 35b545332b80 ("gpio: remove gpio_lock")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Adrian Ambrozewicz <aambrozewicz@nvidia.com>
---
 drivers/gpio/gpiolib.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index faf4a8507dd6..49b2823dab0c 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2669,7 +2669,12 @@ void gpiod_free_commit(struct gpio_desc *desc)
 
 	flags = READ_ONCE(desc->flags);
 
-	if (guard.gc && test_bit(GPIOD_FLAG_REQUESTED, &flags)) {
+	if (guard.gc && !test_bit(GPIOD_FLAG_REQUESTED, &flags))
+		return;
+
+	desc_set_label(desc, NULL);
+
+	if (guard.gc) {
 		if (guard.gc->free)
 			guard.gc->free(guard.gc, gpiod_hwgpio(desc));
 
@@ -2688,7 +2693,6 @@ void gpiod_free_commit(struct gpio_desc *desc)
 #ifdef CONFIG_OF_DYNAMIC
 		WRITE_ONCE(desc->hog, NULL);
 #endif
-		desc_set_label(desc, NULL);
 		WRITE_ONCE(desc->flags, flags);
 #ifdef CONFIG_GPIO_CDEV
 		WRITE_ONCE(desc->debounce_period_us, 0);
-- 
2.43.0