On Wed, Apr 05, 2017 at 09:17:25PM +0100, David Howells wrote:
> From: Chun-Yi Lee <jlee@xxxxxxxx>
>
> 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. Prohibit those functions when the kernel is
> locked down.
>
> Signed-off-by: Chun-Yi Lee <jlee@xxxxxxxx>
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> cc: netdev@xxxxxxxxxxxxxxx
> ---
>
> kernel/trace/bpf_trace.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index cee9802cf3e0..7fde851f207b 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -65,6 +65,11 @@ BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr)
> {
> int ret;
>
> + if (kernel_is_locked_down()) {
> + memset(dst, 0, size);
> + return -EPERM;
> + }
this will obviously break the program. How about disabling loading tracing
programs during the lockdown completely?
Also is there a description of what this lockdown trying to accomplish?
The cover letter is scarce in details.
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