6.17-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit 9085e56501d93af9f2d7bd16f7fcfacdde47b99c ]
Use RCU in ip6_xmit() in order to use dst_dev_rcu() to prevent possible UAF.
Fixes: 4a6ce2b6f2ec ("net: introduce a new function dst_dev_put()") Signed-off-by: Eric Dumazet edumazet@google.com Reviewed-by: David Ahern dsahern@kernel.org Link: https://patch.msgid.link/20250828195823.3958522-4-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv6/ip6_output.c | 35 +++++++++++++++++++++-------------- 1 file changed, 21 insertions(+), 14 deletions(-)
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 1e1410237b6ef..e234640433d6b 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -268,35 +268,36 @@ bool ip6_autoflowlabel(struct net *net, const struct sock *sk) int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6, __u32 mark, struct ipv6_txoptions *opt, int tclass, u32 priority) { - struct net *net = sock_net(sk); const struct ipv6_pinfo *np = inet6_sk(sk); struct in6_addr *first_hop = &fl6->daddr; struct dst_entry *dst = skb_dst(skb); - struct net_device *dev = dst_dev(dst); struct inet6_dev *idev = ip6_dst_idev(dst); struct hop_jumbo_hdr *hop_jumbo; int hoplen = sizeof(*hop_jumbo); + struct net *net = sock_net(sk); unsigned int head_room; + struct net_device *dev; struct ipv6hdr *hdr; u8 proto = fl6->flowi6_proto; int seg_len = skb->len; - int hlimit = -1; + int ret, hlimit = -1; u32 mtu;
+ rcu_read_lock(); + + dev = dst_dev_rcu(dst); head_room = sizeof(struct ipv6hdr) + hoplen + LL_RESERVED_SPACE(dev); if (opt) head_room += opt->opt_nflen + opt->opt_flen;
if (unlikely(head_room > skb_headroom(skb))) { - /* Make sure idev stays alive */ - rcu_read_lock(); + /* idev stays alive while we hold rcu_read_lock(). */ skb = skb_expand_head(skb, head_room); if (!skb) { IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS); - rcu_read_unlock(); - return -ENOBUFS; + ret = -ENOBUFS; + goto unlock; } - rcu_read_unlock(); }
if (opt) { @@ -358,17 +359,21 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6, * skb to its handler for processing */ skb = l3mdev_ip6_out((struct sock *)sk, skb); - if (unlikely(!skb)) - return 0; + if (unlikely(!skb)) { + ret = 0; + goto unlock; + }
/* hooks should never assume socket lock is held. * we promote our socket to non const */ - return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, - net, (struct sock *)sk, skb, NULL, dev, - dst_output); + ret = NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, + net, (struct sock *)sk, skb, NULL, dev, + dst_output); + goto unlock; }
+ ret = -EMSGSIZE; skb->dev = dev; /* ipv6_local_error() does not require socket lock, * we promote our socket to non const @@ -377,7 +382,9 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
IP6_INC_STATS(net, idev, IPSTATS_MIB_FRAGFAILS); kfree_skb(skb); - return -EMSGSIZE; +unlock: + rcu_read_unlock(); + return ret; } EXPORT_SYMBOL(ip6_xmit);