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

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Message-ID: <20250114140729.GQ5388@noisy.programming.kicks-ass.net>
Date: Tue, 14 Jan 2025 15:07:29 +0100
From: Peter Zijlstra <peterz@...radead.org>
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>, 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>,
	Andrii Nakryiko <andrii.nakryiko@...il.com>,
	"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 01:32:58PM +0100, Oleg Nesterov wrote:

> Sorry, I don't understand... Perhaps because I am enjoying my state after
> dentist appointment ;)

For some reason I thought to remember that parent thread would spawn
restricted child, however:

> OK, suppose we have
> 
> 	void start_SECCOMP_MODE_STRICT(void)
> 	{
> 		// in particular nacks __NR_uretprobe
> 		seccomp(SECCOMP_MODE_STRICT, ...);
> 	}
> 
> and we want to add uretprobe to this function.
> 
> In this case prepare_uretprobe() can't know that sys_uretprobe() won't
> work when this function returns?

Indeed. But any further probes placed after seccomp() would be able to,
and installing trampolines for them would be a waste, no?