From 363c8c79220d0db4d65dcd570529ddda15067cb5 Mon Sep 17 00:00:00 2001 From: Kaho Jiang Date: Wed, 21 Oct 2026 19:57:33 -0400 Subject: net: ipv4: add zero check for snd_cwnd_clamp When RTAX_CWND is locked, user is able to pass 0 into it. This could lead to writing 0 to tp->snd_cwnd, leading to a division by zero error. 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 and if lock is present. Fixes: 814d488c6126 ("tcp: fix the timid additive increase on stretch ACKs") Cc: stable@vger.kernel.org Suggested-by: Eric Dumazet Reported-by: co+71b6509cb791e531@bugs.sh Signed-off-by: Kaho Jiang Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20261021235732.1313305-2-kj2864@nyu.edu Signed-off-by: Paolo Abeni --- net/ipv4/metrics.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'net') diff --git a/net/ipv4/metrics.c b/net/ipv4/metrics.c index ad40762a8b38..4052a90249c6 100644 --- a/net/ipv4/metrics.c +++ b/net/ipv4/metrics.c @@ -60,6 +60,11 @@ static int ip_metrics_convert(struct nlattr *fc_mx, if (ecn_ca) metrics[RTAX_FEATURES - 1] |= DST_FEATURE_ECN_CA; + if ((metrics[RTAX_LOCK - 1] & (1 << RTAX_CWND)) && !metrics[RTAX_CWND - 1]) { + NL_SET_ERR_MSG(extack, "Locked cwnd metric must be non zero"); + return -EINVAL; + } + return 0; } -- cgit v1.2.3