On Mon, 21 Aug 2023 10:29:43 -0400
Steven Rostedt [off-list ref] wrote:
On Sun, 20 Aug 2023 03:02:18 -0700
Song Liu [off-list ref] wrote:
quoted
quoted
For the "unique symbol" + offset, you don't need the kallsyms, but need to
access the System.map or vmlinux image. In this case, we don't need to expand
the CAP_PERFMON capabilities.
I agree this is not needed in this case. But I wonder whether it makes sense
to give CAP_PERFMON access to /proc/kallsyms. Will this change make
CAP_PERFMON less secure?
I guess the question is, does CAP_PERFMON allow seeing where the kernel
mapped itself via some other means? If not, then no, I would nack this as
being a security hole.
As Song said, CAP_PERFMON allows user to put a kprobe anywhere user specified,
and it can run BPF program on it. This means it can access raw address
information via registers. if so, CAP_PERFMON allows seeing the kernel map or
equivalent information at this point.
-- Steve
--
Masami Hiramatsu (Google) [off-list ref]