Re: [libgpiod][PATCH v2] core: check for positive values returned by calls to ioctl()

[Kent Gibson <warthog618@xxxxxxxxx>]

On Thu, Jan 25, 2024 at 09:06:29AM +0100, Bartosz Golaszewski wrote:
> 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.
>
> 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@xxxxxxxxxxx>
> Fixes: b7ba732e6a93 ("treewide: libgpiod v2 implementation")
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>

Reviewed-by: Kent Gibson <warthog618@xxxxxxxxx>