Re: An actual suggestion (Re: [GIT PULL] Kernel lockdown for secure boot)

joeyli
2018-04-05T01:48:20Z

On Wed, Apr 04, 2018 at 11:19:27PM +0100, David Howells wrote:
> Jann Horn <jannh@google.com> wrote:
>
> > > Uh, no. bpf, for example, can be used to modify kernel memory.
> >
> > I'm pretty sure bpf isn't supposed to be able to modify arbitrary
> > kernel memory. AFAIU if you can use BPF to write to arbitrary kernel
> > memory, that's a bug; with CAP_SYS_ADMIN, you can read from userspace,
> > write to userspace, and read from kernelspace, but you shouldn't be
> > able to write to kernelspace.
>
> Ah - you may be right. I seem to have misremembered what Joey Lee wrote in
> his patch description.
>

Sorry for it's my fault to misunderstood the behavoir of bpf with
CAP_SYS_ADMIN.

Joey Lee