Re: [PATCH v4 10/11] seccomp: Switch addfd to Extensible Argument ioctl

Tycho Andersen
2020-06-16T14:56:03Z

On Mon, Jun 15, 2020 at 08:25:23PM -0700, Kees Cook wrote:
> This patch is based on discussions[1] with Sargun Dhillon, Christian
> Brauner, and David Laight. Instead of building size into the addfd
> structure, make it a function of the ioctl command (which is how sizes are
> normally passed to ioctls). To support forward and backward compatibility,
> just mask out the direction and size, and match everything. The size (and
> any future direction) checks are done along with copy_struct_from_user()
> logic. Also update the selftests to check size bounds.
>
> [1] https://lore.kernel.org/lkml/20200612104629.GA15814@ircssh-2.c.rugged-nimbus-611.internal
>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> include/uapi/linux/seccomp.h | 2 -
> kernel/seccomp.c | 21 ++++++----
> tools/testing/selftests/seccomp/seccomp_bpf.c | 40 ++++++++++++++++---
> 3 files changed, 49 insertions(+), 14 deletions(-)
>
> diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h
> index c347160378e5..473a61695ac3 100644
> --- a/include/uapi/linux/seccomp.h
> +++ b/include/uapi/linux/seccomp.h
> @@ -118,7 +118,6 @@ struct seccomp_notif_resp {
>
> /**
> * struct seccomp_notif_addfd
> - * @size: The size of the seccomp_notif_addfd structure
> * @id: The ID of the seccomp notification
> * @flags: SECCOMP_ADDFD_FLAG_*
> * @srcfd: The local fd number
> @@ -126,7 +125,6 @@ struct seccomp_notif_resp {
> * @newfd_flags: The O_* flags the remote FD should have applied
> */
> struct seccomp_notif_addfd {
> - __u64 size;

Huh? Won't this break builds?

Tycho