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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Nikolay Borisov <nborisov@suse.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Peter Zijlstra <peterz@infradead.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Masami Hiramatsu <mhiramat@kernel.org>, bpf <bpf@vger.kernel.org>,
	Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH bpf] bpf: Unbreak BPF_PROG_TYPE_KPROBE when kprobe is called via do_int3
Date: Tue, 2 Feb 2021 23:11:06 -0800	[thread overview]
Message-ID: <CAADnVQ+mDa+m=qnbHAT2v_rknESrrc5GL8Z3i6TOK0BwhzydyA@mail.gmail.com> (raw)
In-Reply-To: <baf2f6f5-9e0d-e09d-1030-f20288618e20@suse.com>

On Tue, Feb 2, 2021 at 11:09 PM Nikolay Borisov <nborisov@suse.com> wrote:
>
>
>
> On 3.02.21 г. 9:06 ч., Alexei Starovoitov wrote:
> > From: Alexei Starovoitov <ast@kernel.org>
> >
> > The commit 0d00449c7a28 ("x86: Replace ist_enter() with nmi_enter()")
> > converted do_int3 handler to be "NMI-like".
> > That made old if (in_nmi()) check abort execution of bpf programs
> > attached to kprobe when kprobe is firing via int3
> > (For example when kprobe is placed in the middle of the function).
> > Remove the check to restore user visible behavior.
> >
> > Fixes: 0d00449c7a28 ("x86: Replace ist_enter() with nmi_enter()")
> > Reported-by: Nikolay Borisov <nborisov@suse.com>
> > Signed-off-by: Alexei Starovoitov <ast@kernel.org>
>
> Tested-by: Nikolay Borisov <nborisov@suse.com>
>
>
> So I take it you have verified the callpaths and deemed that it's safe
> to remove this check?

I stared a lot into different places. It's not pretty. I will follow up with
tightening patches for bpf-next, but I couldn't come up with anything
better for bpf tree.

  reply	other threads:[~2021-02-03  7:12 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-03  7:06 [PATCH bpf] bpf: Unbreak BPF_PROG_TYPE_KPROBE when kprobe is called via do_int3 Alexei Starovoitov
2021-02-03  7:09 ` Nikolay Borisov
2021-02-03  7:11   ` Alexei Starovoitov [this message]
2021-02-03 12:40 ` Masami Hiramatsu
2021-02-03 20:40 ` patchwork-bot+netdevbpf

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