6.12-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit a527750d877fd334de87eef81f1cb5f0f0ca3373 ]
mld_newpack() can be called without RTNL or RCU being held.
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 edumazet@google.com Reviewed-by: David Ahern dsahern@kernel.org Link: https://patch.msgid.link/20250212141021.1663666-1-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv6/mcast.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c index 6551648512585..b7b62e5a562e5 100644 --- a/net/ipv6/mcast.c +++ b/net/ipv6/mcast.c @@ -1730,21 +1730,19 @@ static struct sk_buff *mld_newpack(struct inet6_dev *idev, unsigned int mtu) struct net_device *dev = idev->dev; int hlen = LL_RESERVED_SPACE(dev); int tlen = dev->needed_tailroom; - struct net *net = dev_net(dev); const struct in6_addr *saddr; struct in6_addr addr_buf; struct mld2_report *pmr; struct sk_buff *skb; unsigned int size; struct sock *sk; - int err; + struct net *net;
- sk = net->ipv6.igmp_sk; /* we assume size > sizeof(ra) here * Also try to not allocate high-order pages for big MTU */ size = min_t(int, mtu, PAGE_SIZE / 2) + hlen + tlen; - skb = sock_alloc_send_skb(sk, size, 1, &err); + skb = alloc_skb(size, GFP_KERNEL); if (!skb) return NULL;
@@ -1752,6 +1750,12 @@ static struct sk_buff *mld_newpack(struct inet6_dev *idev, unsigned int mtu) skb_reserve(skb, hlen); skb_tailroom_reserve(skb, mtu, tlen);
+ rcu_read_lock(); + + net = dev_net_rcu(dev); + sk = net->ipv6.igmp_sk; + skb_set_owner_w(skb, sk); + if (ipv6_get_lladdr(dev, &addr_buf, IFA_F_TENTATIVE)) { /* <draft-ietf-magma-mld-source-05.txt>: * use unspecified address as the source address @@ -1763,6 +1767,8 @@ static struct sk_buff *mld_newpack(struct inet6_dev *idev, unsigned int mtu)
ip6_mc_hdr(sk, skb, dev, saddr, &mld2_all_mcr, NEXTHDR_HOP, 0);
+ rcu_read_unlock(); + skb_put_data(skb, ra, sizeof(ra));
skb_set_transport_header(skb, skb_tail_pointer(skb) - skb->data);