[libgpiod][PATCH] core: ignore positive values returned by the GPIO_V2_GET_LINE ioctl()

[Bartosz Golaszewski <brgl@xxxxxxxx>]

From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>

If the kernel GPIO driver (erroneously) returns a positive value from one
of its callbacks, it may end up being propagated to user space as
a positive value returned by the call to ioctl(). Let's treat all
non-zero values as errors as GPIO uAPI ioctl()s are not expected to ever
return positive values. This should be addressed in the kernel but will
remain a problem on older or unpatched versions so we need to sanitize it
in user-space too.

Reported-by: José Guilherme de Castro Rodrigues <joseguilhermebh@xxxxxxxxxxx>
Fixes: b7ba732e6a93 ("treewide: libgpiod v2 implementation")
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
---
 lib/chip.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/chip.c b/lib/chip.c
index 7c05e53..7bf40c6 100644
--- a/lib/chip.c
+++ b/lib/chip.c
@@ -239,7 +239,7 @@ gpiod_chip_request_lines(struct gpiod_chip *chip,
 		return NULL;
 
 	ret = ioctl(chip->fd, GPIO_V2_GET_LINE_IOCTL, &uapi_req);
-	if (ret < 0)
+	if (ret)
 		return NULL;
 
 	request = gpiod_line_request_from_uapi(&uapi_req, info.name);
-- 
2.40.1