[PATCH] gpiolib: fix stack out-of-bounds write in gpiochip_add_hog()

[Bartosz Golaszewski]

In gpiochip_add_hog(), parsing a device tree with an excessively large
"#gpio-cells" property causes a stack out-of-bounds write when populating
the GPIO specification.

The value read from #gpio-cells is used to copy the values into right
places in struct fwnode_reference_args but that struct's args field is
an array of size NR_FWNODE_REFERENCE_ARGS so a value larger than it will
make the loop write past the end of that array.

Reject #gpio-cells larger than NR_FWNODE_REFERENCE_ARGS.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 802c51a83e9a ("gpiolib: fix hogs with multiple lines")
Closes: https://sashiko.dev/#/bug/linux-fdec1c0e-c6e3-4eb6-8746-d68a3f951374
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
---
 drivers/gpio/gpiolib.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index fbdeda2f278713a47c2e3d2a6640f387f6d92227..698f86fa14591be484f36999e9b578cb4946917e 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -986,6 +986,8 @@ int gpiochip_add_hog(struct gpio_chip *gc, struct fwnode_handle *fwnode)
 	ret = fwnode_property_read_u32(gc_node, "#gpio-cells", &cells);
 	if (ret && is_of_node(fwnode))
 		return ret;
+	if (cells > NR_FWNODE_REFERENCE_ARGS)
+		return -EINVAL;
 	if (argc % cells)
 		return -EINVAL;
 

---
base-commit: 8b7179210b22f8e48a82c5ceacb9d56a9c4cfec4
change-id: 20261105-gpiolib-hog-stack-corruption-431b647ea556

Best regards,
-- 
Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>