linux-kernel - Re: Crash when attaching uretprobes to processes running in Docker

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Message-ID: <CAEf4BzaRCzWMVvyGC_T52djF7q65yM8=AdBEMOPUU8edG-PLxg@mail.gmail.com>
Date: Tue, 14 Jan 2025 13:45:11 -0800
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Jiri Olsa <olsajiri@...il.com>, Aleksa Sarai <cyphar@...har.com>, 
	Eyal Birger <eyal.birger@...il.com>, mhiramat@...nel.org, 
	linux-kernel <linux-kernel@...r.kernel.org>, linux-trace-kernel@...r.kernel.org, 
	BPF-dev-list <bpf@...r.kernel.org>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, 
	John Fastabend <john.fastabend@...il.com>, peterz@...radead.org, tglx@...utronix.de, 
	bp@...en8.de, x86@...nel.org, linux-api@...r.kernel.org, 
	Andrii Nakryiko <andrii@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Alexei Starovoitov <ast@...nel.org>, "rostedt@...dmis.org" <rostedt@...dmis.org>, rafi@....io, 
	Shmulik Ladkani <shmulik.ladkani@...il.com>
Subject: Re: Crash when attaching uretprobes to processes running in Docker

On Tue, Jan 14, 2025 at 12:40 PM Oleg Nesterov <oleg@...hat.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.
>
>