On 08/07, Dmitry Safonov wrote:
>
> On 8/7/19 4:48 PM, Oleg Nesterov wrote:
> > On 08/06, Adrian Reber wrote:
> >>
> >> @@ -2530,12 +2530,14 @@ noinline static int
> >> copy_clone_args_from_user(struct kernel_clone_args *kargs,
> >> struct clone_args __user *uargs,
> >> size_t size)
> >> {
> >> + struct pid_namespace *pid_ns = task_active_pid_ns(current);
> >> struct clone_args args;
> >>
> >> if (unlikely(size > PAGE_SIZE))
> >> return -E2BIG;
> >>
> >> - if (unlikely(size < sizeof(struct clone_args)))
> >> + /* The struct needs to be at least the size of the original struct. */
> >> + if (size < (sizeof(struct clone_args) - sizeof(__aligned_u64)))
> >> return -EINVAL;
> >
> > slightly off-topic, but with or without this patch I do not understand
> > -EINVAL. Can't we replace this check with
> >
> > if (size < sizeof(struct clone_args))
> > memset((void*)&args + size, sizeof(struct clone_args) - size,
> > 0);
> >
> > ?
> >
> > this way we can new members at the end of clone_args and this matches
> > the "if (size > sizeof(struct clone_args))" block below which promises
> > that whatever we add into clone_args a zero value should work.
>
> What if the size is lesser than offsetof(struct clone_args, stack_size)?
> Probably, there should be still a check that it's not lesser than what's
> the required minimum..
Not sure I understand... I mean, this doesn't differ from the case when
size == sizeof(clone_args) but uargs->stack == NULL ?
> Also note, that (kargs) and (args) are a bit different beasts in this
> context..
> kargs lies on the stack and might want to be with zero-initializer
> : struct kernel_clone_args kargs = {};
I don't think so. Lets consider this patch which adds the new set_tid
into clone_args and kernel_clone_args. copy_clone_args_from_user() does
*kargs = (struct kernel_clone_args){
.flags = args.flags,
.pidfd = u64_to_user_ptr(args.pidfd),
.child_tid = u64_to_user_ptr(args.child_tid),
.parent_tid = u64_to_user_ptr(args.parent_tid),
.exit_signal = args.exit_signal,
.stack = args.stack,
.stack_size = args.stack_size,
.tls = args.tls,
};
so this patch should simply add
.set_tid = args.set_tid;
at the end. No?
Oleg.
