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

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Message-ID: <CAHsH6Gs03iJt-ziWt5Bye_DuqCbk3TpMmgPbkYh64XBvpGaDtw@mail.gmail.com>
Date: Wed, 15 Jan 2025 05:24:22 -0800
From: Eyal Birger <eyal.birger@...il.com>
To: Jiri Olsa <olsajiri@...il.com>
Cc: Oleg Nesterov <oleg@...hat.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

Hi,

On Wed, Jan 15, 2025 at 1:36 AM Jiri Olsa <olsajiri@...il.com> wrote:
>
> 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

Sounds reasonable to me.
I'm wondering how hard it is to figure out the seccomp installation
given that from what I understand it's inherited.

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

I'm wondering when one would enable/disable such sysctl.
"Give me speed but potentially crash processes I don't control"
is a curious semantic...

Eyal

>
> jirka