Re: [PATCH v1 2/4] clone3: switch to copy_struct_from_user()

Christian Brauner
2019-09-25T17:22:36Z

On Wed, Sep 25, 2019 at 06:59:13PM +0200, Aleksa Sarai wrote:
> The change is very straightforward, and helps unify the syscall
> interface for struct-from-userspace syscalls. Additionally, explicitly
> define CLONE_ARGS_SIZE_VER0 to match the other users of the
> struct-extension pattern.
>
> Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
> ---
> include/uapi/linux/sched.h | 2 ++
> kernel/fork.c | 34 +++++++---------------------------
> 2 files changed, 9 insertions(+), 27 deletions(-)
>
> diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h
> index b3105ac1381a..0945805982b4 100644
> --- a/include/uapi/linux/sched.h
> +++ b/include/uapi/linux/sched.h
> @@ -47,6 +47,8 @@ struct clone_args {
> __aligned_u64 tls;
> };
>
> +#define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */
> +
> /*
> * Scheduling policies
> */
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 541fd805fb88..a86e3841ee4e 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -2530,39 +2530,19 @@ SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
> #ifdef __ARCH_WANT_SYS_CLONE3
> noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
> struct clone_args __user *uargs,
> - size_t size)
> + size_t usize)
> {
> + int err;
> struct clone_args args;
>
> - if (unlikely(size > PAGE_SIZE))
> + if (unlikely(usize > PAGE_SIZE))
> return -E2BIG;
> -
> - if (unlikely(size < sizeof(struct clone_args)))
> + if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
> return -EINVAL;

You might want to rebase this patchset after the merge window closes on
rc1 since that code has changed right before the 5.3 release. But if you
can't don't worry I can also fix it up.

Christian