From 4322dcde6b4173c2d8e8e6118ed290794263bcc8 Mon Sep 17 00:00:00 2001 From: Zhengchuan Liang Date: Wed, 13 May 2026 15:57:17 +0800 Subject: [PATCH] netfilter: ip6t_hbh: reject oversized option lists struct ip6t_opts stores at most IP6T_OPTS_OPTSNR option descriptors, but hbh_mt6_check() does not reject larger optsnr values supplied from userspace. Validate optsnr in the rule setup path so only match data that fits the fixed-size opts array can be installed. This follows the existing xtables pattern of rejecting invalid user-provided counts in checkentry() and keeps the packet matching path unchanged. `struct ip6t_opts` has a fixed `opts[IP6T_OPTS_OPTSNR]` array, where `IP6T_OPTS_OPTSNR` is 16, then off-by-one array access is possible: [ 137.924693][ T8692] UBSAN: array-index-out-of-bounds in ../net/ipv6/netfilter/ip6t_hbh.c:110:29 [ 137.926167][ T8692] index 16 is out of range for type '__u16 [16]' Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@kernel.org Reported-by: Yuan Tan Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Xin Liu Signed-off-by: Zhengchuan Liang Signed-off-by: Ren Wei Signed-off-by: Pablo Neira Ayuso --- net/ipv6/netfilter/ip6t_hbh.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv6/netfilter/ip6t_hbh.c b/net/ipv6/netfilter/ip6t_hbh.c index e7a3fb9355ee..450dd53846a2 100644 --- a/net/ipv6/netfilter/ip6t_hbh.c +++ b/net/ipv6/netfilter/ip6t_hbh.c @@ -168,6 +168,10 @@ static int hbh_mt6_check(const struct xt_mtchk_param *par) pr_debug("unknown flags %X\n", optsinfo->invflags); return -EINVAL; } + if (optsinfo->optsnr > IP6T_OPTS_OPTSNR) { + pr_debug("too many supported opts specified\n"); + return -EINVAL; + } if (optsinfo->flags & IP6T_OPTS_NSTRICT) { pr_debug("Not strict - not implemented");