[PATCH net] ipv6: fix possible UAF in icmpv6_rcv()

Eric Dumazet
2026-04-16T10:35:09Z

Caching saddr and daddr before pskb_pull() is problematic
since skb->head can change.

Remove these temporary variables:

- We only access &ipv6_hdr(skb)->saddr and &ipv6_hdr(skb)->daddr
when net_dbg_ratelimited() is called in the slow path.

- Avoid potential future misuse after pskb_pull() call.

Fixes: 4b3418fba0fe ("ipv6: icmp: include addresses in debug messages")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
net/ipv6/icmp.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 799d9e9ac45d11f7b460da7d8a7aeeaf0eb50f2f..efb23807a0262e8d68aa1afc8d96ee94eab89d50 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -1104,7 +1104,6 @@ static int icmpv6_rcv(struct sk_buff *skb)
struct net *net = dev_net_rcu(skb->dev);
struct net_device *dev = icmp6_dev(skb);
struct inet6_dev *idev = __in6_dev_get(dev);
- const struct in6_addr *saddr, *daddr;
struct icmp6hdr *hdr;
u8 type;

@@ -1135,12 +1134,10 @@ static int icmpv6_rcv(struct sk_buff *skb)

__ICMP6_INC_STATS(dev_net_rcu(dev), idev, ICMP6_MIB_INMSGS);

- saddr = &ipv6_hdr(skb)->saddr;
- daddr = &ipv6_hdr(skb)->daddr;
-
if (skb_checksum_validate(skb, IPPROTO_ICMPV6, ip6_compute_pseudo)) {
net_dbg_ratelimited("ICMPv6 checksum failed [%pI6c > %pI6c]\n",
- saddr, daddr);
+ &ipv6_hdr(skb)->saddr,
+ &ipv6_hdr(skb)->daddr);
goto csum_error;
}

@@ -1220,7 +1217,8 @@ static int icmpv6_rcv(struct sk_buff *skb)
break;

net_dbg_ratelimited("icmpv6: msg of unknown type [%pI6c > %pI6c]\n",
- saddr, daddr);
+ &ipv6_hdr(skb)->saddr,
+ &ipv6_hdr(skb)->daddr);

/*
* error of unknown type.
--
2.54.0.rc1.513.gad8abe7a5a-goog