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ipv6: mcast: extend RCU protection in igmp6_send()

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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: b8ad0cbc58 ("[NETNS][IPV6] mcast - handle several network namespace")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250207135841.1948589-9-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2025-02-07 13:58:40 +00:00 • committed by Jakub Kicinski
parent ed6ae1f325
commit 087c1faa59
1 changed files with 15 additions and 16 deletions
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31
net/ipv6/mcast.c
View file

@ -2165,21 +2165,21 @@ 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;
@ -2190,19 +2190,21 @@ 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;
skb = alloc_skb(hlen + tlen + full_len, GFP_KERNEL);
rcu_read_lock();
IP6_INC_STATS(net, __in6_dev_get(dev), IPSTATS_MIB_OUTREQUESTS);
rcu_read_unlock();
skb = sock_alloc_send_skb(sk, hlen + tlen + full_len, 1, &err);
net = dev_net_rcu(dev);
idev = __in6_dev_get(dev);
IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTREQUESTS);
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);
@ -2227,9 +2229,6 @@ 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);