From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-170.mta1.migadu.com (out-170.mta1.migadu.com [95.215.58.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8737B3630B5 for ; Tue, 21 Apr 2026 15:59:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776787161; cv=none; b=bzAVtLEhzer7XGkB/gGq/qtna6Ov/fXlV5by6+iVxmj/qK3PPaumNd3Y/JLLqMFXSleFX4CZQX9RJHWP1B7JXHWvvekpJxiUcY1hhgsccn45xAunUvEFRITW61/ddwqhGffgsmsqjkJBSfVbHD+V83CsD4k7beloEYh9juHO8y4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776787161; c=relaxed/simple; bh=MASmzLLYx8bP7k5KvtnKIA/J9TSasL0lOIuwGyJ/+7g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BJs62EajFNXveP1Aozmmf+aVU8BmfULa9vt6mtgFMtzDr9q6jo64U4PHM3ffX4M/QJ6CXnUMgQL85M0pdH0mNu7/0qe3IyQuEsa+hL0zMP0MZjh7eEWKoea9iZTTalWHDBekar3JRbx6VVSXKs3r3EUG4XCf6dF7OsiKwkIVp3M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=DWyyV3jM; arc=none smtp.client-ip=95.215.58.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="DWyyV3jM" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1776787157; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4FXbVn3w1/0ZWZKtjjV1fGo1JJvX0eigdezJlZf0mPI=; b=DWyyV3jMcOMdC0EmdqPxblY+4mvPESGFDAqc+ig3S481VnOVlcQq8ps3g66z8vJHJ4hn2P 1JHKrBX6mWHNYGOENSq7DL7NhkF+7gFJd2/REPcFdpNIUhppUNjVO6GHOiqxHOcBr4/6qT 2vdSvsqGbo97DTQ7DORzzTROtnt58dk= From: KaFai Wan To: ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, memxor@gmail.com, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, sdf@fomichev.me, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, dsahern@kernel.org, shuah@kernel.org, ihor.solodrai@linux.dev, kafai.wan@linux.dev, jiayuan.chen@linux.dev, hoyeon.lee@suse.com, ameryhung@gmail.com, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: Quan Sun <2022090917019@std.uestc.edu.cn>, Yinhao Hu , Kaiyan Mei Subject: [PATCH bpf-next v4 1/4] bpf: Reject TCP_NODELAY in TCP header option callbacks Date: Tue, 21 Apr 2026 23:58:01 +0800 Message-ID: <20260421155804.135786-2-kafai.wan@linux.dev> In-Reply-To: <20260421155804.135786-1-kafai.wan@linux.dev> References: <20260421155804.135786-1-kafai.wan@linux.dev> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 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 Reported-by: Kaiyan Mei 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") Reviewed-by: Jiayuan Chen Signed-off-by: KaFai Wan --- net/core/filter.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/core/filter.c b/net/core/filter.c index 5fa9189eb772..96849f4c1fbc 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5833,6 +5833,12 @@ BPF_CALL_5(bpf_sock_ops_setsockopt, struct bpf_sock_ops_kern *, bpf_sock, if (!is_locked_tcp_sock_ops(bpf_sock)) return -EOPNOTSUPP; + /* TCP_NODELAY triggers tcp_push_pending_frames() and re-enters these callbacks. */ + if ((bpf_sock->op == BPF_SOCK_OPS_HDR_OPT_LEN_CB || + bpf_sock->op == BPF_SOCK_OPS_WRITE_HDR_OPT_CB) && + level == SOL_TCP && optname == TCP_NODELAY) + return -EOPNOTSUPP; + return _bpf_setsockopt(bpf_sock->sk, level, optname, optval, optlen); } -- 2.43.0