Re: [PATCH bpf-next v5 0/9] tools: bpftool: add probes for system and device

On Thu, Jan 17, 2019 at 7:28 AM Quentin Monnet
[off-list ref] wrote:

If the user does not have root privileges (or more precisely, the
CAP_SYS_ADMIN capability) detection will be erroneous for most
parameters. Therefore, forbid non-root users to run the command.

v5:
- Move exported symbols to a new LIBBPF_0.0.2 section in libbpf.map
  (patches 4 to 6).
- Minor fixes on patches 3 and 4.

I was about to apply the set,
but while testing on older kernels bpftool crashed the box.
It's a kernel bug, no doubt, but bpftool shouldn't be doing
dangerous operations if it can potentially crash it.
I'm debugging what went wrong.
It crashed after this message:
CONFIG_XFRM is set to y
dmesg was:
[1757577.380114] BUG: unable to handle kernel
[1757577.388476] NULL pointer dereference
[1757577.395957]  at           (null)
[1757577.402752] IP:           (null)
[1757577.421265] Call Trace:
[1757577.421269]  ? SyS_bpf+0x18b/0x16b0
[1757577.421272]  ? __audit_syscall_entry+0xb5/0x100
[1757577.421277]  do_syscall_64+0x53/0x150
Not sure how that was possible.
I'm still debugging.