Re: [PATCH 5/6] lib: Fix function documentation for strncpy_from_user

From: Kees Cook
Date: Thu Feb 21 2019 - 17:52:40 EST


On Thu, Feb 21, 2019 at 6:28 AM Jann Horn <jannh@xxxxxxxxxx> wrote:
> On Thu, Feb 21, 2019 at 2:05 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> > On Mon, Feb 18, 2019 at 4:52 PM Jann Horn <jannh@xxxxxxxxxx> wrote:
> > > AFAICS the byte_at_a_time loop exits when max==0 is reached, and then
> > > if `res >= count` (in other words, if we've copied as many bytes as
> > > requested, haven't encountered a null byte so far, and haven't reached
> > > the end of the address space), we return `res`, which is the same as
> > > `count`. Are you sure?
> >
> > Oh, whew, there is only 1 arch-specific implementation of this. I
> > thought you meant there was multiple implementations.
>
> Not sure what you're talking about. Are you talking about
> implementations of strncpy_from_user()?

Ah, I used a bad match. But it seems it's only about half (and not
x86, arm, powerpc).

--
Kees Cook