Re: Crash when attaching uretprobes to processes running in Docker

Andrii Nakryiko
2025-01-14T21:45:25Z

On Tue, Jan 14, 2025 at 12:40 PM Oleg Nesterov <oleg@redhat.com> wrote:
>
> On 01/14, Andrii Nakryiko wrote:
> >
> > Should we just fix whoever is blocking kernel-internal special syscall
> > (sys_uretprobe)?
>
> Well, we can add __NR_uretprobe to mode1_syscalls[] but this won't
> really help.
>
> We can't "fix" the existing user-space setups which can nack any
> "unnecessary/unknown" syscall.
>
> > What would happen if someone blocked that other
> > special kernel-internal syscall for signal handling (can't remember
> > the name,
>
> sys_rt_sigreturn().
>
> Yes, the task will crash after return from the signal handler if this
> syscall is filtered out.
>
> But, unlike sys_uretprobe(), sys_rt_sigreturn() is old, so the existing
> setups must know that sigreturn() should be respected...

someday sys_uretprobe will be old as well ;) FWIW, systemd allowlisted
sys_uretprobe, see [0]

[0] https://github.com/systemd/systemd/issues/34615#issuecomment-2406761451

>
> Oleg.
>
>