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[216.165.95.175]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-5362aa19a3asm2389211cf.24.2026.10.15.13.16.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Oct 2026 13:16:24 -0700 (PDT) From: Kaho Jiang To: ncardwell@google.com, kuniyu@google.com, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, edumazet@google.com Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, co+71b6509cb791e531@bugs.sh, Kaho Jiang , stable@vger.kernel.org Subject: [PATCH net v3] net: ipv4: add zero check for snd_cwnd_clamp Date: Thu, 15 Oct 2026 16:15:50 -0400 Message-ID: <20261015201549.4023-2-kj2864@nyu.edu> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Proofpoint-Spam-Info: AW1haW4tMjYxMDE1MDA4MCBTYWx0ZWRfXyunA1IHqc2XJ dj8rWy6mfzft8aYq0NZfR1Ay5qRzZ+tUovukHPdREDhSWBkxJttH6hyWgVdBZhHQqmIW9x+ANEr JWsAZYuLPvdd1UnRv/FoRVrz9HVYqZI= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDE1MDA4MCBTYWx0ZWRfX6Jl11qfMljBi z3jCARUfgpXiaVKaFLYc3tBL4D3BcqRuK6aftVl7QQb/DYO6f5N2/s5JiVRIuGr52YO2a6MeSqo OVI4UlbKzPAabX0JfQS24y7VxD8zHiv1SHvFW4U8Y2FsZ0NPt8SlV2oUtb0hYdILqlPPoQpti5M pS5dibmUWznaQXE8nV4WKgSKYB14rb55w+eZ0fMyebHvV0QIu4x4+AZboQNMgGHnIbZoUcntTdu 1Lccb8P5oPdwJNtpT1jJ7EPNGlYg3JImBhK0SGzVXl1JG0UVCinGrQlkEvmpeuoU+yp8H1cyTZi xftaWExe3H6VO8kTShPQq3n2tMTssFvO/ZeJw7HSH4eSm6nu/gUbsPOyZwx7/iwpOZQG5pRGLMl fmxwoPQSLQsJYbqZKGTLG+EeFvOWqaTDqYyCZQzZ571yq/BLaOsAAvID5DLjxdfbnBeDJ5uSKxa jQ13v6vce7UJbdz3Eng== X-Proofpoint-ORIG-GUID: z1c1B2LXyrqOmy3Rlu-QBuuMxtGcUmiq X-Proofpoint-GUID: z1c1B2LXyrqOmy3Rlu-QBuuMxtGcUmiq X-Authority-Analysis: v=2.4 cv=ZZGIpcVA c=1 sm=1 tr=0 ts=6ad1349b cx=c_pps a=JbAStetqSzwMeJznSMzCyw==:117 a=HR2R1zjsIcTlYEo9jw4mrw==:17 a=660iZSQnnn4A:10 a=x7bEGLp0ZPQA:10 a=S0S_EcBMpFAA:10 a=VkNPw1HP01LnGYTKEx00:22 a=Se5WoFf3ZZRiLcel0nel:22 a=Lu3rmdZLeA08KL8VqJdF:22 a=VwQbUJbxAAAA:8 a=qtVHbROC6xTCA7o1MbIA:9 a=uxP6HrT_eTzRwkO_Te1X:22 X-Orig-IP: 209.85.160.200 X-Proofpoint-Spam-Details: rule=outbound_bp_notspam policy=outbound_bp score=0 clxscore=1015 suspectscore=0 spamscore=0 malwarescore=0 bulkscore=0 lowpriorityscore=0 phishscore=0 priorityscore=1501 adultscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610080000 definitions=main-2610150080 Content-Type: text/plain; charset="utf-8" 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/netfilte= r.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) ./inclu= de/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 (discriminat= or 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 --- net/ipv4/metrics.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv4/metrics.c b/net/ipv4/metrics.c index ad40762a8b38..e83a129a25b6 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 att= ribute"); return -EINVAL; } + if (type =3D=3D RTAX_CWND && val =3D=3D 0) { + NL_SET_ERR_MSG(extack, "RTAX_CWND must be greater than zero"); + return -EINVAL; + } metrics[type - 1] =3D val; } =20 --=20 2.43.0