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 use the default value of snd_cwnd_clamp. Fixes: 51c5d0c4b169 ("tcp: Maintain dynamic metrics in local cache.") Cc: stable@vger.kernel.org Reported-by: co+71b6509cb791e531@bugs.sh Assisted-by: LLM Signed-off-by: Kaho Jiang --- net/ipv4/tcp_metrics.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c index dc0c081fc1f3..ff41804ad086 100644 --- a/net/ipv4/tcp_metrics.c +++ b/net/ipv4/tcp_metrics.c @@ -484,8 +484,11 @@ void tcp_init_metrics(struct sock *sk) goto reset; } - if (tcp_metric_locked(tm, TCP_METRIC_CWND)) - tp->snd_cwnd_clamp = tcp_metric_get(tm, TCP_METRIC_CWND); + if (tcp_metric_locked(tm, TCP_METRIC_CWND)) { + val = tcp_metric_get(tm, TCP_METRIC_CWND); + if (val) + tp->snd_cwnd_clamp = val; + } val = READ_ONCE(net->ipv4.sysctl_tcp_no_ssthresh_metrics_save) ? 0 : tcp_metric_get(tm, TCP_METRIC_SSTHRESH); -- 2.43.0