[PATCH AUTOSEL 6.4 16/17] gpiolib: fix reference leaks when removing GPIO chips still in use

Sasha Levin
2023-08-29T13:35:20Z

From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

[ Upstream commit 3386fb86ecdef0d39ee3306aea8ec290e61b934f ]

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 <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpio/gpiolib.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 5be8ad61523eb..6e7701f80929f 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2175,12 +2175,18 @@ 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 {
+ /*
+ * We must not use VALIDATE_DESC_VOID() as the underlying gdev->chip
+ * may already be NULL but we still want to put the references.
+ */
+ if (!desc)
+ return;
+
+ if (!gpiod_free_commit(desc))
WARN_ON(extra_checks);
- }
+
+ module_put(desc->gdev->owner);
+ gpio_device_put(desc->gdev);
}

/**
--
2.40.1