Re: [PATCH v5 bpf-next 2/3] bpf: implement CAP_BPF

On Tuesday, May 12, 2020 2:36 AM, Alexei Starovoitov [off-list ref] wrote:

On Mon, May 11, 2020 at 05:12:10PM -0700, sdf@google.com wrote:

quoted

On 05/08, Alexei Starovoitov wrote:

quoted

From: Alexei Starovoitov ast@kernel.org
[..]

@@ -3932,7 +3977,7 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr

__user *, uattr, unsigned int, siz
union bpf_attr attr;
int err;

quoted

-   if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN))

-   if (sysctl_unprivileged_bpf_disabled && !bpf_capable())
    return -EPERM;
    This is awesome, thanks for reviving the effort!

One question I have about this particular snippet:
Does it make sense to drop bpf_capable checks for the operations
that work on a provided fd?

Above snippet is for the case when sysctl switches unpriv off.
It was a big hammer and stays big hammer.
I certainly would like to improve the situation, but I suspect
the folks who turn that sysctl knob on are simply paranoid about bpf
and no amount of reasoning would turn them around.

Without CAP_BPF, sysctl was the only option to keep you safe from flow
of bpf vulns. You didn't had to be paranoid about that.

Jordan