Re: null pointer questions

[Ken Ashcraft]

> > 2. What happens if I pass a null pointer as the destination parameter
> > to copy_from_user?  Does copy_from_user handle it safely or will the
> > kernel seg fault?
>
> The kernel won't crash, but it might fail (depending on whether 0 is a
> valid user space address or not).

Why does it matter if 0 is a valid user space or not?  If I make the call

copy_from_user(0, user_ptr, 4);

the null pointer is the kernel address, not the user address.  Can you
clarify please?

Thanks
Ken