From: Luxiao Xu rt_mt6_check() permits rules to be configured with rtinfo->addrnr == 0 even when address matching (IP6T_RT_FST_MASK) is requested. In the IP6T_RT_FST_NSTRICT path, rt_mt6() evaluates packet routing addresses against rtinfo->addrs[i] and terminates backwards at the bottom of the loop: if (ipv6_addr_equal(ap, &rtinfo->addrs[i])) { i++; } if (i == rtinfo->addrnr) break; When addrnr is 0, if the first packet address matches rtinfo->addrs[0], i is incremented to 1. Because i is now strictly greater than addrnr (0), the loop termination condition (i == rtinfo->addrnr) is bypassed and will never be satisfied. If a crafted IPv6 packet contains matching routing addresses, i will advance past IP6T_RT_HOPS (16). The subsequent call to ipv6_addr_equal() reads beyond struct ip6t_rt, triggering UBSAN/KASAN out-of-bounds warnings or kernel panics. Fix this by: 1. Rejecting rules in rt_mt6_check() where IP6T_RT_FST_MASK is set but rtinfo->addrnr is zero. 2. In rt_mt6(), moving the termination condition (i < rtinfo->addrnr) into the for-loop header condition and removing the backwards break at the end of the loop body. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Reported-by: Vega Suggested-by: Florian Westphal Assisted-by: LLM Signed-off-by: Luxiao Xu Signed-off-by: Ren Wei Signed-off-by: Pablo Neira Ayuso --- net/ipv6/netfilter/ip6t_rt.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/net/ipv6/netfilter/ip6t_rt.c b/net/ipv6/netfilter/ip6t_rt.c index 8051425213dd..9880faf3cc7d 100644 --- a/net/ipv6/netfilter/ip6t_rt.c +++ b/net/ipv6/netfilter/ip6t_rt.c @@ -96,7 +96,8 @@ static bool rt_mt6(const struct sk_buff *skb, struct xt_action_param *par) unsigned int i = 0; for (temp = 0; - temp < (unsigned int)((hdrlen - 8) / 16); + temp < (unsigned int)((hdrlen - 8) / 16) && + i < rtinfo->addrnr; temp++) { ap = skb_header_pointer(skb, ptr @@ -112,8 +113,6 @@ static bool rt_mt6(const struct sk_buff *skb, struct xt_action_param *par) if (ipv6_addr_equal(ap, &rtinfo->addrs[i])) i++; - if (i == rtinfo->addrnr) - break; } if (i == rtinfo->addrnr) return ret; @@ -162,6 +161,12 @@ static int rt_mt6_check(const struct xt_mtchk_param *par) pr_info_ratelimited("too many addresses specified\n"); return -EINVAL; } + + if ((rtinfo->flags & IP6T_RT_FST_MASK) && !rtinfo->addrnr) { + pr_info_ratelimited("address list match requested but addrnr is 0\n"); + return -EINVAL; + } + if ((rtinfo->flags & (IP6T_RT_RES | IP6T_RT_FST_MASK)) && (!(rtinfo->flags & IP6T_RT_TYP) || (rtinfo->rt_type != 0) || -- 2.47.3