On Wed, May 29, 2019 at 05:42:14PM +0200, Yann Droneaud wrote:
> Le mercredi 29 mai 2019 à 17:22 +0200, Christian Brauner a écrit :
> > This adds the clone3 system call.
> >
> >
> > diff --git a/kernel/fork.c b/kernel/fork.c
> > index b4cba953040a..6bc3e3d17150 100644
> > --- a/kernel/fork.c
> > +++ b/kernel/fork.c
> > @@ -2472,7 +2475,96 @@ SYSCALL_DEFINE5(clone, unsigned long, clone_flags,
> > unsigned long, newsp,
> > unsigned long, tls)
> > #endif
> > {
> > - return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr,
> > tls);
> > + struct kernel_clone_args args = {
> > + .flags = clone_flags,
> > + .stack = newsp,
> > + .pidfd = parent_tidptr,
> > + .parent_tidptr = parent_tidptr,
> > + .tls = tls,
> > + .child_tidptr = child_tidptr,
> > + };
> > +
> > + /* clone(CLONE_PIDFD) uses parent_tidptr to return a pidfd */
> > + if ((clone_flags & CLONE_PIDFD) && (clone_flags & CLONE_PARENT_SETTID))
> > + return -EINVAL;
> > +
> > + return _do_fork(&args);
> > +}
> > +
> > +static bool clone3_flags_valid(u64 flags)
> > +{
> > + if (flags & CLONE_DETACHED)
> > + return false;
> > +
> > + if (flags & ~CLONE_MAX)
> > + return false;
> > +
> > + return true;
> > +}
> > +
> > +static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
> > + struct clone_args __user *uargs,
> > + size_t size)
> > +{
> > + struct clone_args args;
> > +
> > + if (unlikely(size > PAGE_SIZE))
> > + return -E2BIG;
> > +
> > + if (unlikely(size < sizeof(struct clone_args)))
> > + return -EINVAL;
> > +
> > + if (unlikely(!access_ok(uargs, size)))
> > + return -EFAULT;
> > +
> > + if (size > sizeof(struct clone_args)) {
> > + unsigned char __user *addr;
> > + unsigned char __user *end;
> > + unsigned char val;
> > +
> > + addr = (void __user *)uargs + sizeof(struct clone_args);
> > + end = (void __user *)uargs + size;
> > +
> > + for (; addr < end; addr++) {
> > + if (get_user(val, addr))
> > + return -EFAULT;
> > + if (val)
> > + return -E2BIG;
>
> Should be -EINVAL: having something after the structure should be
> handled just like an invalid flags, while still allowing future
> userspace program to probe for support for newer feature.
(Traveling until Monday, so sorry for delayed responses.)
This copies what:
kernel/sched/core.c:sched_copy_attr()
kernel/event/core.c:perf_copy_attr()
are already doing. Consistency might be good here but, I think.
Christian
