From: Yiqi Sun Date: Thu, 2 Apr 2026 07:04:19 +0000 (+0800) Subject: ipv4: icmp: fix null-ptr-deref in icmp_build_probe() X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fde29fd9349327acc50d19a0b5f3d5a6c964dfd8;p=thirdparty%2Flinux.git ipv4: icmp: fix null-ptr-deref in icmp_build_probe() ipv6_stub->ipv6_dev_find() may return ERR_PTR(-EAFNOSUPPORT) when the IPv6 stack is not active (CONFIG_IPV6=m and not loaded), and passing this error pointer to dev_hold() will cause a kernel crash with null-ptr-deref. Instead, silently discard the request. RFC 8335 does not appear to define a specific response for the case where an IPv6 interface identifier is syntactically valid but the implementation cannot perform the lookup at runtime, and silently dropping the request may safer than misreporting "No Such Interface". Fixes: d329ea5bd884 ("icmp: add response to RFC 8335 PROBE messages") Signed-off-by: Yiqi Sun Link: https://patch.msgid.link/20260402070419.2291578-1-sunyiqixm@gmail.com Signed-off-by: Jakub Kicinski --- diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c index 568bd1e95d44..4e2a6c70dcd8 100644 --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -1346,6 +1346,13 @@ bool icmp_build_probe(struct sk_buff *skb, struct icmphdr *icmphdr) if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in6_addr)) goto send_mal_query; dev = ipv6_stub->ipv6_dev_find(net, &iio->ident.addr.ip_addr.ipv6_addr, dev); + /* + * If IPv6 identifier lookup is unavailable, silently + * discard the request instead of misreporting NO_IF. + */ + if (IS_ERR(dev)) + return false; + dev_hold(dev); break; #endif