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(iot-shnota-vm.priv.miraclelinux.com [10.2.1.238]) by smtp.priv.miraclelinux.com (Postfix) with ESMTP id 19DCC140074; Wed, 16 Sep 2026 17:13:14 +0900 (JST) From: Shun Ota To: stable@vger.kernel.org Cc: netdev@vger.kernel.org, Eric Dumazet , David Ahern , Kuniyuki Iwashima , Jakub Kicinski , Shun Ota Subject: [PATCH 5.10.y 5.15.y 6.1.y] ipv6: mcast: extend RCU protection in igmp6_send() Date: Wed, 16 Sep 2026 17:12:32 +0900 Message-ID: <20260916081232.326250-1-shun.ota@miraclelinux.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Eric Dumazet [ Upstream commit 087c1faa594fa07a66933d750c0b2610aa1a2946 ] igmp6_send() can be called without RTNL or RCU being held. Extend RCU protection so that we can safely fetch the net pointer and avoid a potential UAF. Note that we no longer can use sock_alloc_send_skb() because ipv6.igmp_sk uses GFP_KERNEL allocations which can sleep. Instead use alloc_skb() and charge the net->ipv6.igmp_sk socket under RCU protection. Fixes: b8ad0cbc58f7 ("[NETNS][IPV6] mcast - handle several network namespace") Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250207135841.1948589-9-edumazet@google.com Signed-off-by: Jakub Kicinski [ use IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_OUT, full_len) instead of upstream's IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTPKTS). Older LTS kernels do not have commit b4a11b2033b7 ("net: fix IPSTATS_MIB_OUTPKGS increment in OutForwDatagrams"), so the legacy byte-based counter logic must be preserved. ] Signed-off-by: Shun Ota --- net/ipv6/mcast.c | 32 +++++++++++++++----------------- 1 file changed, 15 insertions(+), 17 deletions(-) diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c index c4a9866ea45b..7b141c227eef 100644 --- a/net/ipv6/mcast.c +++ b/net/ipv6/mcast.c @@ -2146,21 +2146,21 @@ static void mld_send_cr(struct inet6_dev *idev) static void igmp6_send(struct in6_addr *addr, struct net_device *dev, int type) { - struct net *net = dev_net(dev); - struct sock *sk = net->ipv6.igmp_sk; + const struct in6_addr *snd_addr, *saddr; + int err, len, payload_len, full_len; + struct in6_addr addr_buf; struct inet6_dev *idev; struct sk_buff *skb; struct mld_msg *hdr; - const struct in6_addr *snd_addr, *saddr; - struct in6_addr addr_buf; int hlen = LL_RESERVED_SPACE(dev); int tlen = dev->needed_tailroom; - int err, len, payload_len, full_len; u8 ra[8] = { IPPROTO_ICMPV6, 0, IPV6_TLV_ROUTERALERT, 2, 0, 0, IPV6_TLV_PADN, 0 }; - struct flowi6 fl6; struct dst_entry *dst; + struct flowi6 fl6; + struct net *net; + struct sock *sk; if (type == ICMPV6_MGM_REDUCTION) snd_addr = &in6addr_linklocal_allrouters; @@ -2171,20 +2171,21 @@ static void igmp6_send(struct in6_addr *addr, struct net_device *dev, int type) payload_len = len + sizeof(ra); full_len = sizeof(struct ipv6hdr) + payload_len; - rcu_read_lock(); - IP6_UPD_PO_STATS(net, __in6_dev_get(dev), - IPSTATS_MIB_OUT, full_len); - rcu_read_unlock(); + skb = alloc_skb(hlen + tlen + full_len, GFP_KERNEL); - skb = sock_alloc_send_skb(sk, hlen + tlen + full_len, 1, &err); + rcu_read_lock(); + net = dev_net_rcu(dev); + idev = __in6_dev_get(dev); + IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_OUT, full_len); if (!skb) { - rcu_read_lock(); - IP6_INC_STATS(net, __in6_dev_get(dev), - IPSTATS_MIB_OUTDISCARDS); + IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS); rcu_read_unlock(); return; } + sk = net->ipv6.igmp_sk; + skb_set_owner_w(skb, sk); + skb->priority = TC_PRIO_CONTROL; skb_reserve(skb, hlen); @@ -2209,9 +2210,6 @@ static void igmp6_send(struct in6_addr *addr, struct net_device *dev, int type) IPPROTO_ICMPV6, csum_partial(hdr, len, 0)); - rcu_read_lock(); - idev = __in6_dev_get(skb->dev); - icmpv6_flow_init(sk, &fl6, type, &ipv6_hdr(skb)->saddr, &ipv6_hdr(skb)->daddr, skb->dev->ifindex); -- 2.43.0