Re: [PATCH 23/27] bpf: Restrict kernel image access functions when the kernel is locked down

[Stephen Hemminger]

On Mon, 25 Mar 2019 16:42:21 -0700
Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx> wrote:

> On Mon, 25 Mar 2019 15:09:50 -0700
> Matthew Garrett <matthewgarrett@xxxxxxxxxx> wrote:
> 
> > From: David Howells <dhowells@xxxxxxxxxx>
> > 
> > There are some bpf functions can be used to read kernel memory:
> > bpf_probe_read, bpf_probe_write_user and bpf_trace_printk.  These allow
> > private keys in kernel memory (e.g. the hibernation image signing key) to
> > be read by an eBPF program and kernel memory to be altered without
> > restriction.
> > 
> > Completely prohibit the use of BPF when the kernel is locked down.
> > 
> > Suggested-by: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>
> > Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> > cc: netdev@xxxxxxxxxxxxxxx
> > cc: Chun-Yi Lee <jlee@xxxxxxxx>
> > cc: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>
> > Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> > Signed-off-by: Matthew Garrett <matthewgarrett@xxxxxxxxxx>  
> 
> Wouldn't this mean that Seccomp won't work in locked down mode?

Never mind. This is about bpf system call, not locking out all bpf in general.