Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nfnetlink_osf: fix divide-by-zero in OSF_WSS_MODULO nf_osf_match_one() computes ctx->window % f->wss.val in the OSF_WSS_MODULO branch with no guard for f->wss.val == 0. A CAP_NET_ADMIN user can add such a fingerprint via nfnetlink; a subsequent matching TCP SYN divides by zero and panics the kernel. Reject the bogus fingerprint in nfnl_osf_add_callback() above the per-option for-loop. f->wss is per-fingerprint, not per-option, so the check must run regardless of f->opt_num (including 0). Also reject wss.wc >= OSF_WSS_MAX; nf_osf_match_one() already treats that as "should not happen". Crash: Oops: divide error: 0000 [#1] SMP KASAN NOPTI RIP: 0010:nf_osf_match_one (net/netfilter/nfnetlink_osf.c:98) Call Trace: <IRQ> nf_osf_match (net/netfilter/nfnetlink_osf.c:220) xt_osf_match_packet (net/netfilter/xt_osf.c:32) ipt_do_table (net/ipv4/netfilter/ip_tables.c:348) nf_hook_slow (net/netfilter/core.c:622) ip_local_deliver (net/ipv4/ip_input.c:265) ip_rcv (include/linux/skbuff.h:1162) __netif_receive_skb_one_core (net/core/dev.c:6181) process_backlog (net/core/dev.c:6642) __napi_poll (net/core/dev.c:7710) net_rx_action (net/core/dev.c:7945) handle_softirqs (kernel/softirq.c:622)

References 8

• git.kernel.org https://git.kernel.org/stable/c/0694618cf3e9b120666e31f5f383a6e466d95a0d
• git.kernel.org https://git.kernel.org/stable/c/2195574dc6d9017d32ac346987e12659f931d932
• git.kernel.org https://git.kernel.org/stable/c/26900306a5a2c3e4f75c643a064525526bb6e5f3
• git.kernel.org https://git.kernel.org/stable/c/8def8fbd23f40e945febe913d04b731012ce0082
• git.kernel.org https://git.kernel.org/stable/c/9a05e195618a6d474f2bcd5b6376d0ffc2f00366
• git.kernel.org https://git.kernel.org/stable/c/c55940895245d8ef658ab381248a28755218d625
• git.kernel.org https://git.kernel.org/stable/c/cb833bbc1b3c51e08652d3c86298307c07d3f2db
• git.kernel.org https://git.kernel.org/stable/c/fb965b1cfe92b28d28b5ebe3116b81dbef9f2d2f

Remediation