On 5/13/20 9:24 PM, John Fastabend wrote:
Often it is useful when applying policy to know something about the
task. If the administrator has CAP_SYS_ADMIN rights then they can
use kprobe + sk_msg and link the two programs together to accomplish
this. However, this is a bit clunky and also means we have to call
sk_msg program and kprobe program when we could just use a single
program and avoid passing metadata through sk_msg/skb, socket, etc.
To accomplish this add probe_* helpers to sk_msg programs guarded
by a CAP_SYS_ADMIN check. New supported helpers are the following,
BPF_FUNC_get_current_task
BPF_FUNC_current_task_under_cgroup
BPF_FUNC_probe_read_user
BPF_FUNC_probe_read_kernel
BPF_FUNC_probe_read
BPF_FUNC_probe_read_user_str
BPF_FUNC_probe_read_kernel_str
BPF_FUNC_probe_read_str
Given the current discussion in the other thread with Linus et al, please
don't add more users for BPF_FUNC_probe_read and BPF_FUNC_probe_read_str
as I'm cooking up a patch to disable them on non-x86, and cleanups from
Christoph would make them less efficient than the *_user/_kernel{,_str}()
versions anyway, so lets only add the latter.
Thanks,
Daniel
