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

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Message-ID: <CAHsH6Gu1kXZ=m3eoTeZcZ9n=n2scxw7z074PnY5oTsXfTqZ=vQ@mail.gmail.com>
Date: Wed, 15 Jan 2025 10:48:06 -0800
From: Eyal Birger <eyal.birger@...il.com>
To: Oleg Nesterov <oleg@...hat.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 Wed, Jan 15, 2025 at 10:40 AM Oleg Nesterov <oleg@...hat.com> wrote:
>
> On 01/15, Alexei Starovoitov wrote:
> >
> > On Wed, Jan 15, 2025 at 7:06 AM Oleg Nesterov <oleg@...hat.com> wrote:
> > >
> > > Or we can change __secure_computing() to do nothing if
> > > this_syscall == __NR_uretprobe.
> >
> > I think that's the best way forward.
> > seccomp already allowlists sigreturn syscall.
>
> Only if SECCOMP_MODE_STRICT. But it won't help if we add __NR_uretprobe
> into into mode1_syscalls/mode1_syscalls_32.
>
> SECCOMP_MODE_FILTER can do anything. Just I guess nobody tries to offend
> sigreturn for obvious reasons.
>
> But yes, perhaps we do not have a better solution.
>

Indeed - doing the check in __secure_computing_strict() doesn't seem to be
enough.

In __secure_computing(), i.e. the below hack it works.

Eyal.

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 385d48293a5f..5739482036ce 100644
--- 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;
+
        switch (mode) {
        case SECCOMP_MODE_STRICT:
                __secure_computing_strict(this_syscall);  /* may call do_exit */