Re: AUDIT: copy_from_user is a deathtrap.

[Alan Cox]

> > must return PAGE_SIZE on an error. What it seems to say is that it if an error
> > is reported then no data got written down the actual pipe itself. Putting
> > 4K into the pipe then reporting Esomething is not allowed. Copying 4K into
> > a buffer faulting and erroring with Efoo then throwing away the buffer is
> > allowed
> 
> So... Is copy_to_user allowed to copy more than it actually reported?
> Because if so, it might return 0/-EFAULT as well ;-).

The specification defines the API not the implementation. It only matters if
the user can't tell. 0/-EFAULT would be wrong as that is EOF. 0/0 or
-1/Efoo.