Re: [RFC][PATCH 3/7] kprobes: Remove kretprobe hash

peterz
2020-08-28T13:59:53Z

On Fri, Aug 28, 2020 at 10:51:13PM +0900, Masami Hiramatsu wrote:

> OK, schedule function will be the key. I guess the senario is..
>
> 1) kretporbe replace the return address with kretprobe_trampoline on task1's kernel stack
> 2) the task1 forks task2 before returning to the kretprobe_trampoline
> 3) while copying the process with the kernel stack, task2->kretprobe_instances.first = NULL
> 4) task2 returns to the kretprobe_trampoline
> 5) Bomb!
>
> Hmm, we need to fixup the kernel stack when copying process.

How would that scenario have been avoided in the old code? Because there
task2 would have a different has and not have found a kretprobe_instance
either.