Re: [RFC PATCH 2/4] trace: Allow kprobes to override livepatched functions

[Steven Rostedt <rostedt@goodmis.org>]

On Fri, 03 Apr 2026 18:25:59 +0800
Menglong Dong <menglong.dong@linux.dev> wrote:

> I think the security problem is a big issue. Image that we have a KLP
> in our environment. Any users can crash the kernel by hook a BPF
> program on it with the calling of bpf_override_write().

Right, livepatching may allow for rapid experimentation but that is not its
purpose. It is for fixing production systems without having to reboot.
Using BPF to change the return of a function is a huge security issue.

> 
> What's more, this is a little weird for me. If we allow to use bpf_override_return()
> for the kernel functions in a KLP, why not we allow it in a common kernel
> module, as KLP is a kind of kernel module. Then, why not we allow to
> use it for all the kernel functions?

Right.

> 
> Can we mark the "bond_get_slave_hook" with ALLOW_ERROR_INJECTION() in
> your example? Then we can override its return directly. This is a more
> reasonable for me. With ALLOW_ERROR_INJECTION(), we are telling people that
> anyone can modify the return of this function safely.

If this were to go in, I say it would require both a kernel config, with
a big warning about this being a security hole, and a kernel command line
option to enable it, so that people don't accidentally have it enabled in
their config.

The command line should be something like:

  allow_bpf_to_rootkit_functions

-- Steve