netdev - Re: [PATCH bpf 2/2] bpf: Require ARG_PTR_TO

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Message-Id: <774A6E90-11F3-4EEB-B6DD-210FD4CAB267@gmail.com>
Date: Wed, 7 Jan 2026 20:58:58 +0800
From: Zesen Liu <ftyghome@...il.com>
To: Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 Andrii Nakryiko <andrii@...nel.org>,
 Martin KaFai Lau <martin.lau@...ux.dev>,
 Eduard Zingerman <eddyz87@...il.com>,
 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@...ichev.me>,
 Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>,
 Matt Bobrowski <mattbobrowski@...gle.com>,
 Steven Rostedt <rostedt@...dmis.org>,
 Masami Hiramatsu <mhiramat@...nel.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>,
 Simon Horman <horms@...nel.org>,
 Daniel Xu <dxu@...uu.xyz>
Cc: bpf@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org,
 netdev@...r.kernel.org,
 Shuran Liu <electronlsr@...il.com>,
 Peili Gao <gplhust955@...il.com>,
 Haoran Ni <haoran.ni.cs@...il.com>
Subject: Re: [PATCH bpf 2/2] bpf: Require ARG_PTR_TO_MEM with memory flag

Hi,

It seems my mail server blocked the cover letter (0/2) of this patchset. Please ignore this thread, I will resend the complete series.
Sorry for the noise.

Thanks,
Zesen Liu

> On Jan 7, 2026, at 20:16, Zesen Liu <ftyghome@...il.com> wrote:
> 
> Add check to ensure that ARG_PTR_TO_MEM is used with either MEM_WRITE or
> MEM_RDONLY.
> 
> Using ARG_PTR_TO_MEM alone without tags does not make sense because:
> 
> - If the helper does not change the argument, missing MEM_RDONLY causes the
> verifier to incorrectly reject a read-only buffer.
> - If the helper does change the argument, missing MEM_WRITE causes the
> verifier to incorrectly assume the memory is unchanged, leading to errors
> in code optimization.
> 
> Co-developed-by: Shuran Liu <electronlsr@...il.com>
> Signed-off-by: Shuran Liu <electronlsr@...il.com>
> Co-developed-by: Peili Gao <gplhust955@...il.com>
> Signed-off-by: Peili Gao <gplhust955@...il.com>
> Co-developed-by: Haoran Ni <haoran.ni.cs@...il.com>
> Signed-off-by: Haoran Ni <haoran.ni.cs@...il.com>
> Signed-off-by: Zesen Liu <ftyghome@...il.com>
> ---
> kernel/bpf/verifier.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
> 
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index f0ca69f888fa..c7ebddb66385 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -10349,10 +10349,27 @@ static bool check_btf_id_ok(const struct bpf_func_proto *fn)
> return true;
> }
> 
> +static bool check_mem_arg_rw_flag_ok(const struct bpf_func_proto *fn)
> +{
> + int i;
> +
> + for (i = 0; i < ARRAY_SIZE(fn->arg_type); i++) {
> + enum bpf_arg_type arg_type = fn->arg_type[i];
> +
> + if (base_type(arg_type) != ARG_PTR_TO_MEM)
> + continue;
> + if (!(arg_type & (MEM_WRITE | MEM_RDONLY)))
> + return false;
> + }
> +
> + return true;
> +}
> +
> static int check_func_proto(const struct bpf_func_proto *fn, int func_id)
> {
> return check_raw_mode_ok(fn) &&
>       check_arg_pair_ok(fn) &&
> +   check_mem_arg_rw_flag_ok(fn) &&
>       check_btf_id_ok(fn) ? 0 : -EINVAL;
> }
> 
> 
> -- 
> 2.43.0
>