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[216.165.95.129]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-91bcbb0b231sm56350806d6.31.2026.10.17.14.49.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 17 Oct 2026 14:49:03 -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 v4] net: ipv4: add zero check for snd_cwnd_clamp Date: Sat, 17 Oct 2026 17:48:46 -0400 Message-ID: <20261017214845.28769-2-kj2864@nyu.edu> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDE3MDA4NyBTYWx0ZWRfX/O6mdXepe9SI CabZVY/hBxLNfiQUae7IWH8pMfpeIjV2KiKAYcU3M+/B2Rrz3ETkDo5uKUUt2eDEk12VeKkIk/T BSBRmgHEf3ml7AS1Y+duD0xhgwWSj2QVw0cKdFw/0eoUWDtUuEIZ8LPymiB6G3+j/zmRvdKeO+t e0J74sw7xr5XXJ9D+IJC1QvPdTiKsGARTvJZb+SDtbhH2wbCKDI9wyKGtq4Ahp75mcsk8crbCjK ZO2ZB6ozdgMEzEkUdflV1VMnjchE80ZZd6SxzuwlJ1oyuEybEpw6jAAkszXd35aaMQW+duTMlZk GmeghEfaEP9dzUQ8ZsVTpm4GAHljZFRKfu/E2sGf8uvtOt7SDTiOpFJDG3rAvkrkYKKsRPMLTim GExj2oIIPfQGnQ7YQSDUwr6WblxuSCNH5sB0SvtIeNqhPeNWtTYJiiGc2wvitE09rossn47fVFd q9jVlicWbT2PaaGlPzw== X-Proofpoint-GUID: z5_HQG9HOKOhJPFtRAO_DU-TBGs9MUDi X-Authority-Analysis: v=2.4 cv=C+58WgP+ c=1 sm=1 tr=0 ts=6ad3ed52 cx=c_pps a=WeENfcodrlLV9YRTxbY/uA==:117 a=k9NFnU9fOQnGI6ew/wxyRQ==:17 a=660iZSQnnn4A:10 a=x7bEGLp0ZPQA:10 a=S0S_EcBMpFAA:10 a=VkNPw1HP01LnGYTKEx00:22 a=Se5WoFf3ZZRiLcel0nel:22 a=tr4woWNwjDflhTIOjkZU:22 a=VwQbUJbxAAAA:8 a=qtVHbROC6xTCA7o1MbIA:9 a=kacYvNCVWA4VmyqE58fU:22 X-Proofpoint-ORIG-GUID: z5_HQG9HOKOhJPFtRAO_DU-TBGs9MUDi X-Proofpoint-Spam-Info: AW1haW4tMjYxMDE3MDA4NyBTYWx0ZWRfX0WbGUKXT5vtl aJts/M2vey4KQcaL6OxU47rOGlgTFaIGCzovEucQU78nu+dH6bi6pMKuJeBmKaIZUBOulhxHdZn Rued7/QcWOl7/SCBZ23WTAVdIcyXQp4= X-Orig-IP: 209.85.160.199 X-Proofpoint-Spam-Details: rule=outbound_bp_notspam policy=outbound_bp score=0 clxscore=1015 adultscore=0 malwarescore=0 suspectscore=0 phishscore=0 lowpriorityscore=0 impostorscore=0 spamscore=0 priorityscore=1501 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610080000 definitions=main-2610170087 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)); } 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