From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Jiri Olsa <olsajiri@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
bpf@vger.kernel.org, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Borislav Petkov (AMD)" <bp@alien8.de>,
x86@kernel.org, linux-api@vger.kernel.org
Subject: Re: [PATCHv2 1/3] uprobe: Add uretprobe syscall to speed up return probe
Date: Fri, 5 Apr 2024 10:22:03 +0900 [thread overview]
Message-ID: <20240405102203.825c4a2e9d1c2be5b2bffe96@kernel.org> (raw)
In-Reply-To: <20240404161108.GG7153@redhat.com>
On Thu, 4 Apr 2024 18:11:09 +0200
Oleg Nesterov <oleg@redhat.com> wrote:
> On 04/05, Masami Hiramatsu wrote:
> >
> > Can we make this syscall and uprobe behavior clearer? As you said, if
> > the application use sigreturn or longjump, it may skip returns and
> > shadow stack entries are left in the kernel. In such cases, can uretprobe
> > detect it properly, or just crash the process (or process runs wrongly)?
>
> Please see the comment in handle_trampoline(), it tries to detect this case.
> This patch should not make any difference.
I think you mean this loop will skip and discard the stacked return_instance
to find the valid one.
----
do {
/*
* We should throw out the frames invalidated by longjmp().
* If this chain is valid, then the next one should be alive
* or NULL; the latter case means that nobody but ri->func
* could hit this trampoline on return. TODO: sigaltstack().
*/
next = find_next_ret_chain(ri);
valid = !next || arch_uretprobe_is_alive(next, RP_CHECK_RET, regs);
instruction_pointer_set(regs, ri->orig_ret_vaddr);
do {
if (valid)
handle_uretprobe_chain(ri, regs);
ri = free_ret_instance(ri);
utask->depth--;
} while (ri != next);
} while (!valid);
----
I think this expects setjmp/longjmp as below
foo() { <- retprobe1
setjmp()
bar() { <- retprobe2
longjmp()
}
} <- return to trampoline
In this case, we need to skip retprobe2's instance.
My concern is, if we can not find appropriate return instance, what happen?
e.g.
foo() { <-- retprobe1
bar() { # sp is decremented
sys_uretprobe() <-- ??
}
}
It seems sys_uretprobe() will handle retprobe1 at that point instead of
SIGILL.
Can we avoid this with below strict check?
if (ri->stack != regs->sp + expected_offset)
goto sigill;
expected_offset should be 16 (push * 3 - ret) on x64 if we ri->stack is the
regs->sp right after call.
Thank you,
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
next prev parent reply other threads:[~2024-04-05 1:22 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20240402093302.2416467-1-jolsa@kernel.org>
[not found] ` <20240402093302.2416467-2-jolsa@kernel.org>
[not found] ` <20240403100708.233575a8ac2a5bac2192d180@kernel.org>
[not found] ` <Zg0lvUIB4WdRUGw_@krava>
[not found] ` <20240403230937.c3bd47ee47c102cd89713ee8@kernel.org>
[not found] ` <CAEf4BzZ2RFfz8PNgJ4ENZ0us4uX=DWhYFimXdtWms-VvGXOjgQ@mail.gmail.com>
[not found] ` <20240404095829.ec5db177f29cd29e849169fa@kernel.org>
[not found] ` <CAEf4BzYH60TwvBipHWB_kUqZZ6D-iUVnnFsBv06imRikK3o-bg@mail.gmail.com>
2024-04-04 15:54 ` [PATCHv2 1/3] uprobe: Add uretprobe syscall to speed up return probe Masami Hiramatsu
2024-04-04 16:11 ` Oleg Nesterov
2024-04-05 1:22 ` Masami Hiramatsu [this message]
2024-04-05 8:56 ` Jiri Olsa
2024-04-05 11:02 ` Oleg Nesterov
2024-04-06 3:05 ` Masami Hiramatsu
2024-04-06 17:55 ` Oleg Nesterov
2024-04-08 3:54 ` Masami Hiramatsu
2024-04-08 16:02 ` Jiri Olsa
2024-04-08 16:22 ` Oleg Nesterov
2024-04-09 12:06 ` Jiri Olsa
2024-04-09 0:34 ` Masami Hiramatsu
2024-04-09 7:57 ` Jiri Olsa
2024-04-08 3:16 ` Masami Hiramatsu
[not found] ` <Zg6V8y2-OP_9at2l@krava>
2024-04-04 16:06 ` Masami Hiramatsu
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