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

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Message-ID: <20250114203922.GA5051@redhat.com>
Date: Tue, 14 Jan 2025 21:39:22 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.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 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...

Oleg.