Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address limit before returning to user-mode

Ingo Molnar
2017-05-12T06:57:33Z

* Kees Cook <keescook@chromium.org> wrote:

> > git commit b5a882fcf146c87cb6b67c6df353e1c042b8773d
> > "s390: restore address space when returning to user space".
>
> If I'm understanding this, it won't catch corruption of addr_limit
> during fast-path syscalls, though (i.e. addr_limit changed without a
> call to set_fs()). :(

Nor does it, or the patch you propose, protect against against something
corrupting task->mm pointer, or the task->*uid values, or any of the myriads of
security relevant values stored in the task structure!

Making sure API (set_fs()) usage is bug-free and protecting against the effects of
general data corruption are two unrelated things that should not mixed.

Thanks,

Ingo