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

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Message-ID: <20250116143956.GD21801@redhat.com>
Date: Thu, 16 Jan 2025 15:39:57 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Eyal Birger <eyal.birger@...il.com>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Jiri Olsa <olsajiri@...il.com>, Aleksa Sarai <cyphar@...har.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-trace-kernel <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>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>, X86 ML <x86@...nel.org>,
	Linux API <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 01/15, Eyal Birger wrote:
>
> On Wed, Jan 15, 2025 at 11:03 AM Oleg Nesterov <oleg@...hat.com> wrote:
> >
> > On 01/15, Eyal Birger wrote:
> > >
> > > --- a/kernel/seccomp.c
> > > +++ b/kernel/seccomp.c
> > > @@ -1359,6 +1359,9 @@ int __secure_computing(const struct seccomp_data *sd)
> > >         this_syscall = sd ? sd->nr :
> > >                 syscall_get_nr(current, current_pt_regs());
> > >
> > > +       if (this_syscall == __NR_uretprobe)
> > > +               return 0;
> > > +
> >
> > Yes, this is what I meant. But we need the new arch-dependent helper.
>
> Do you mean because __NR_uretprobe is not defined for other architectures?

Yes, and see below,

> Is there an existing helper? I wasn't able to find one...

No,

> If not, would it just make sense to just wrap this check in
> #ifdef __NR_uretprobe ?

Given that we need a simple fix for -stable, I won't argue.
Up to seccomp maintainers.

But please note that this_syscall == __NR_uretprobe can be false
positive if is_compat_task().

__NR_uretprobe == __NR_ia32_rt_tgsigqueueinfo, so I guess we need

	#ifdef CONFIG_X86_64
		if (this_syscall == __NR_uretprobe && !in_ia32_syscall())
			return 0;
	#endif

I don't think we need to worry about the X86_X32 tasks...

Oleg.