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

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Message-ID: <Z4eBs0-kJ3iVZjXL@krava>
Date: Wed, 15 Jan 2025 10:36:51 +0100
From: Jiri Olsa <olsajiri@...il.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Jiri Olsa <olsajiri@...il.com>, Eyal Birger <eyal.birger@...il.com>,
	Aleksa Sarai <cyphar@...har.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>,
	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 06:25:20PM +0100, Oleg Nesterov wrote:
> On 01/14, Jiri Olsa wrote:
> >
> > ugh.. could we just 'disable' uretprobe trampoline when seccomp gets enabled?
> > overwrite first byte with int3.. and similarly check on seccomp when installing
> > uretprobe and switch to int3
> 
> Sorry, I don't understand... What exactly we can do? Aside from checking
> IS_ENABLED(CONFIG_SECCOMP) in arch_uprobe_trampoline() ?

I need to check more on seccomp, but I imagine we could do following:
  - when seccomp filter is installed we could check uprobe trampoline
    and if it's already installed we change it to int3 trampoline
  - when uprobe trampoline is getting installed we check if there's
    seccomp filter installed for task and we use int3 trampoline

other than that I guess we will have to add sysctl to enable uretprobe
trampoline..

jirka