netdev - Re: [RFC PATCH bpf-next 1/2] bpf, x64: Fix tailcall infinite loop bug

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Date: Fri, 18 Aug 2023 12:59:24 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Leon Hwang <hffilwlqm@...il.com>
Cc: bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, X86 ML <x86@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, 
	Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>, 
	"David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>, 
	Yizhou Tang <tangyeechou@...il.com>, kernel-patches-bot@...com, 
	"Fijalkowski, Maciej" <maciej.fijalkowski@...el.com>, Network Development <netdev@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>
Subject: Re: [RFC PATCH bpf-next 1/2] bpf, x64: Fix tailcall infinite loop bug

On Thu, Aug 17, 2023 at 7:10 PM Leon Hwang <hffilwlqm@...il.com> wrote:
>
>
>
> On 18/8/23 06:31, Alexei Starovoitov wrote:
> > On Mon, Aug 14, 2023 at 09:41:46PM +0800, Leon Hwang wrote:
> >> @@ -1147,6 +1152,7 @@ struct bpf_attach_target_info {
> >>      struct module *tgt_mod;
> >>      const char *tgt_name;
> >>      const struct btf_type *tgt_type;
> >> +    bool tail_call_ctx;
> >
> > Instead of extra flag here can you check tgt_prog->aux->tail_call_reachable in check_attach_btf_id()
> > and set tr->flags there?
>
> Should we check tgt_prog->aux->func[subprog]->is_func? Or, tgt_prog->aux->tail_call_reachable
> is enough?

Please let the thread continue to a logical conclusion before resending
new version. Will reply there.