From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 D66024534B7; Mon, 19 Oct 2026 08:33:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792398812; cv=none; b=rg0TCht/s9bFkUmwWFQYWLIkxXQIHF0VIWqPMpEjD0ytf6ncwgB/IQBkdegWsdQpa/4XgPQsrztC+G1cjnWvgXIsIzv3oboxLa0Aj8M/Fw1klVGABMBLgM1NpDCq5aXlVIZjEtxEZai3uv4quY/XR6aIuoxspFNtEcymbQmgKfY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792398812; c=relaxed/simple; bh=0tc+7e5ERNzkGutQX1PNSv71eGwmHwj5lPN8UTXoldE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mChcHqhMJbfW4E+OsoNCN1/2FzqA6eTMcAi8mrV1S94jT90vsEdPrsFrA+l6P/aEi7s+axSeUisxgSPsESToneWfE/MqwFiP1ofK8GgDiR9CuePtIEfUJiSIDAUzBsp1rqjH0QHA4I8w3SO2j2tl4vJ89c1HwAiPZxCDuFCnvfU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RWo7jM7H; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="RWo7jM7H" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D13921F000C4; Mon, 19 Oct 2026 08:33:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792398811; bh=IK0sXuhZ5deIdhI5ZoljWsNdq8PHkjbXwO2tF69oNWc=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=RWo7jM7HRYUErWa0ZhfJ/fdtmrVB4NsbND6vQoqgb1ouiW7uRyVmUujGTdjPMpXh0 b7rGi4WihBygFFsgVuTxfYN5O6oeuWepvgAZXlQ6rmUV1gO+ZLcfIr139jPF8m50t9 LlQI6kXYbUFXgANWquIEGG+4OITFL4OssNg7zY/uE8FMODgx1suQd/DhiA1BtL2uHj w+a3TPxGpRz5MVxGU25tBSNuHQzNsZPHfwpskixNPcJkC+54fcispc5v7pmjD15yU+ CmmGjtDDgK/DRORpHK967FCKI3NRcJZoTivqMEKw9J6wLXi67bsqANqDC2Qbi6BXlD +PJ1gWSqfjYkw== Date: Mon, 19 Oct 2026 10:33:28 +0200 From: Antoine Tenart To: Kaho Jiang Cc: ncardwell@google.com, kuniyu@google.com, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, edumazet@google.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, co+71b6509cb791e531@bugs.sh, stable@vger.kernel.org Subject: Re: [PATCH net v4] net: ipv4: add zero check for snd_cwnd_clamp Message-ID: References: <20261017214845.28769-2-kj2864@nyu.edu> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261017214845.28769-2-kj2864@nyu.edu> On Sat, Oct 17, 2026 at 05:48:46PM -0400, Kaho Jiang wrote: > User can pass zero to snd_cwnd_clamp via RTAX_CWND type. > This could lead to division of zero error if not checked properly. > > Oops: divide error: 0000 [#1] SMP KASAN NOPTI > Call Trace: > > tcp_reno_cong_avoid (net/ipv4/tcp_cong.c:510 (discriminator 1)) > tcp_ack (net/ipv4/tcp_input.c:3517 net/ipv4/tcp_input.c:3873 net/ipv4/tcp_input.c:4440) > tcp_rcv_established (net/ipv4/tcp_input.c:6685) > tcp_v4_do_rcv (net/ipv4/tcp_ipv4.c:1854) > tcp_v4_rcv (net/ipv4/tcp_ipv4.c:2248) > ip_protocol_deliver_rcu (net/ipv4/ip_input.c:207 (discriminator 1)) > ip_local_deliver_finish (net/ipv4/ip_input.c:241 (discriminator 1)) > ip_local_deliver (./include/linux/netfilter.h:325 ./include/linux/netfilter.h:319 net/ipv4/ip_input.c:262) > ip_rcv (./include/net/dst.h:481 (discriminator 6) net/ipv4/ip_input.c:492 (discriminator 6) ./include/linux/netfilter.h:325 (discriminator 6) ./include/li) > __netif_receive_skb_one_core (net/core/dev.c:6297 (discriminator 4)) > __netif_receive_skb (net/core/dev.c:6410) > process_backlog (net/core/dev.c:6761) > __napi_poll.constprop.0 (net/core/dev.c:7830) > net_rx_action (net/core/dev.c:7893 net/core/dev.c:8050) > handle_softirqs (kernel/softirq.c:645) > __irq_exit_rcu (kernel/softirq.c:679 kernel/softirq.c:519 kernel/softirq.c:758) > irq_exit_rcu (kernel/softirq.c:775) > sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1062 (discriminator 35) arch/x86/kernel/apic/apic.c:1062 (discriminator 35)) > RIP: 0010:tcp_cong_avoid_ai (net/ipv4/tcp_cong.c:482) > > Fix by checking if user pass in zero as parameter, > if so reject the value zero. > > Fixes: 814d488c6126 ("tcp: fix the timid additive increase on stretch ACKs") > Cc: stable@vger.kernel.org > Reported-by: co+71b6509cb791e531@bugs.sh > Assisted-by: LLM > Signed-off-by: Kaho Jiang > --- > include/net/tcp.h | 3 +-- > net/ipv4/metrics.c | 4 ++++ > 2 files changed, 5 insertions(+), 2 deletions(-) > > diff --git a/include/net/tcp.h b/include/net/tcp.h > index 4416cdf9bf30..ad80b8fb8a52 100644 > --- a/include/net/tcp.h > +++ b/include/net/tcp.h > @@ -1521,8 +1521,7 @@ static inline u32 tcp_snd_cwnd(const struct tcp_sock *tp) > > static inline void tcp_snd_cwnd_set(struct tcp_sock *tp, u32 val) > { > - WARN_ON_ONCE((int)val <= 0); > - WRITE_ONCE(tp->snd_cwnd, val); > + WRITE_ONCE(tp->snd_cwnd, max(val, 1U)); Please keep the warning (it's not only about 0). > } > > static inline bool tcp_in_slow_start(const struct tcp_sock *tp) > diff --git a/net/ipv4/metrics.c b/net/ipv4/metrics.c > index ad40762a8b38..cb36686973e5 100644 > --- a/net/ipv4/metrics.c > +++ b/net/ipv4/metrics.c > @@ -54,6 +54,10 @@ static int ip_metrics_convert(struct nlattr *fc_mx, > NL_SET_ERR_MSG(extack, "Unknown flag set in feature mask in metrics attribute"); > return -EINVAL; > } > + if (type == RTAX_CWND && !val) { > + NL_SET_ERR_MSG(extack, "RTAX_CWND must be greater than zero"); > + return -EINVAL; > + } > metrics[type - 1] = val; > } > > -- > 2.43.0 >