From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-177.mta0.migadu.com (out-177.mta0.migadu.com [91.218.175.177]) (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 B636F39DBE2 for ; Thu, 16 Apr 2026 11:24:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776338666; cv=none; b=kHWzLdE3+i4bBG7zzmsoF20q6qoVTyc+TeQ/QDOIM7fg64E3jbX4+M0cUpFQlPesTLzs1Rk9xMYY9U3c6Kt5tBXtOEiLaME6PA2CMCKAP8oR3xZjZbufv8Kvzs7Wo+0EY6xqZcV2hERK4Cn+G98uZoFnE3Ol4UNnTl/XBTStIQE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776338666; c=relaxed/simple; bh=tGOhrptT9PJ5/cvzp6EKffTU5Kr88yNrPL4dsjtp0/E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uxJN+goL3je3jp/He4ACsZUNvqiz8kjvF9dyxigX81Fb2MhNLY2BrU6pkz6GU9MmgAid6dWFmcNIJP1sPL/xPajZxHzEmrKVVTiGPKk2jjyGOKadq407fmXFBsppRw9incxWF1Cxc1SYXQCHLUimprYTBLwvqkCQF8PVrdvEcoU= 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=UF1KpSD0; arc=none smtp.client-ip=91.218.175.177 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="UF1KpSD0" 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=1776338662; 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=8AldNZMVHS+FDrWsqQWGH6HMzCXTBhC6l0kEDtweIFA=; b=UF1KpSD0RSSqrsSf0EPQ+pdlhKbgUzEbBpVt3z0hBlQ9KX33ed7Ig5M4GtdluxgiCN2NdE NtRnLLXQ+AAm4swHPVKFRRkpN+J2ZGW/ycKIQwiQNJzvTko3F5O3GFRrx+5/FKPmFEY917 a0VVUGPFpWNVuzdxNaUDTio4cDNPofg= From: KaFai Wan To: 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, kafai.wan@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 , Kaiyan Mei Subject: [PATCH bpf v2 1/2] bpf: Reject TCP_NODELAY in TCP header option callbacks Date: Thu, 16 Apr 2026 19:23:07 +0800 Message-ID: <20260416112308.1820332-2-kafai.wan@linux.dev> In-Reply-To: <20260416112308.1820332-1-kafai.wan@linux.dev> References: <20260416112308.1820332-1-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") Signed-off-by: KaFai Wan --- net/core/filter.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/core/filter.c b/net/core/filter.c index fcfcb72663ca..911ff04bca5a 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5833,6 +5833,11 @@ BPF_CALL_5(bpf_sock_ops_setsockopt, struct bpf_sock_ops_kern *, bpf_sock, if (!is_locked_tcp_sock_ops(bpf_sock)) return -EOPNOTSUPP; + if ((bpf_sock->op == BPF_SOCK_OPS_HDR_OPT_LEN_CB || + bpf_sock->op == BPF_SOCK_OPS_WRITE_HDR_OPT_CB) && + IS_ENABLED(CONFIG_INET) && level == SOL_TCP && optname == TCP_NODELAY) + return -EOPNOTSUPP; + return _bpf_setsockopt(bpf_sock->sk, level, optname, optval, optlen); } -- 2.43.0