core: check for positive values returned by calls to ioctl()

core: check for positive values returned by calls to ioctl()

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.

To that end let's create a wrapper around the libc's ioctl() that checks
the return value and sets errno to EBADE (Invalid exchange) if it's
greater than 0.

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@hotmail.com>
Fixes: b7ba732e6a93 ("treewide: libgpiod v2 implementation")
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Kent Gibson <warthog618@gmail.com>