From: Jiayuan Chen <jiayuan.chen@linux.dev>
To: KaFai Wan <kafai.wan@linux.dev>,
martin.lau@linux.dev, daniel@iogearbox.net,
john.fastabend@gmail.com, sdf@fomichev.me, ast@kernel.org,
andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com,
song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org,
davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
pabeni@redhat.com, horms@kernel.org, shuah@kernel.org,
jiayuan.chen@linux.dev, bpf@vger.kernel.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org
Cc: Quan Sun <2022090917019@std.uestc.edu.cn>,
Yinhao Hu <dddddd@hust.edu.cn>,
Kaiyan Mei <M202472210@hust.edu.cn>
Subject: Re: [PATCH bpf v3 1/2] bpf: Reject TCP_NODELAY in TCP header option callbacks
Date: Fri, 17 Apr 2026 18:26:41 +0800 [thread overview]
Message-ID: <0d25b0b7-5560-482c-a626-fc43abb045b3@linux.dev> (raw)
In-Reply-To: <20260417092035.2299913-2-kafai.wan@linux.dev>
On 4/17/26 5:20 PM, KaFai Wan wrote:
> A BPF_SOCK_OPS program can enable
> BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG and then call
> bpf_setsockopt(TCP_NODELAY) from BPF_SOCK_OPS_HDR_OPT_LEN_CB or
> BPF_SOCK_OPS_WRITE_HDR_OPT_CB.
>
> In these callbacks, bpf_setsockopt(TCP_NODELAY) can reach
> __tcp_sock_set_nodelay(), which can call tcp_push_pending_frames().
>
> From BPF_SOCK_OPS_HDR_OPT_LEN_CB, tcp_push_pending_frames() can call
> tcp_current_mss(), which calls tcp_established_options() and re-enters
> bpf_skops_hdr_opt_len().
>
> BPF_SOCK_OPS_HDR_OPT_LEN_CB
> -> bpf_setsockopt(TCP_NODELAY)
> -> tcp_push_pending_frames()
> -> tcp_current_mss()
> -> tcp_established_options()
> -> bpf_skops_hdr_opt_len()
> -> BPF_SOCK_OPS_HDR_OPT_LEN_CB
>
> From BPF_SOCK_OPS_WRITE_HDR_OPT_CB, tcp_push_pending_frames() can call
> tcp_write_xmit(), which calls tcp_transmit_skb(). That path recomputes
> header option length through tcp_established_options() and
> bpf_skops_hdr_opt_len() before re-entering bpf_skops_write_hdr_opt().
>
> BPF_SOCK_OPS_WRITE_HDR_OPT_CB
> -> bpf_setsockopt(TCP_NODELAY)
> -> tcp_push_pending_frames()
> -> tcp_write_xmit()
> -> tcp_transmit_skb()
> -> tcp_established_options()
> -> bpf_skops_hdr_opt_len()
> -> bpf_skops_write_hdr_opt()
> -> BPF_SOCK_OPS_WRITE_HDR_OPT_CB
>
> This leads to unbounded recursion and can overflow the kernel stack.
>
> Reject TCP_NODELAY with -EOPNOTSUPP in bpf_sock_ops_setsockopt()
> when bpf_setsockopt() is called from
> BPF_SOCK_OPS_HDR_OPT_LEN_CB or BPF_SOCK_OPS_WRITE_HDR_OPT_CB.
>
> Reported-by: Quan Sun <2022090917019@std.uestc.edu.cn>
> Reported-by: Yinhao Hu <dddddd@hust.edu.cn>
> Reported-by: Kaiyan Mei <M202472210@hust.edu.cn>
> Closes: https://lore.kernel.org/bpf/d1d523c9-6901-4454-a183-94462b8f3e4e@std.uestc.edu.cn/
> Fixes: 7e41df5dbba2 ("bpf: Add a few optnames to bpf_setsockopt")
> Signed-off-by: KaFai Wan <kafai.wan@linux.dev>
Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>
I think the result of AI review is false-positve.
next prev parent reply other threads:[~2026-04-17 10:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-17 9:20 [PATCH bpf v3 0/2] bpf: Reject TCP_NODELAY in TCP header option callbacks KaFai Wan
2026-04-17 9:20 ` [PATCH bpf v3 1/2] " KaFai Wan
2026-04-17 10:10 ` bot+bpf-ci
2026-04-17 10:26 ` Jiayuan Chen [this message]
2026-04-17 9:20 ` [PATCH bpf v3 2/2] selftests/bpf: Test TCP_NODELAY in TCP hdr opt callbacks KaFai Wan
2026-04-17 10:45 ` Jiayuan Chen
2026-04-17 16:25 ` Martin KaFai Lau
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