Subject: [PATCH net-next 3/3] psp: validate IPv4 header fields in psp_dev_rcv()

From: Jakub Kicinski <[email-masked]>
Date: Tue, 28 Apr 2026 13:53:52 -0700

psp_dev_rcv() is called from the NIC driver's RX completion path
before the frame reaches ip_rcv_core(), so the IP header has not
been validated in SW, yet. We expect that the device has done
all this validation, but let's also add the SW checks, to avoid
surprises.

Signed-off-by: Jakub Kicinski <[email-masked]>
---
 net/psp/psp_main.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/net/psp/psp_main.c b/net/psp/psp_main.c
index f069117c867a..524978dfb8fd 100644
--- a/net/psp/psp_main.c
+++ b/net/psp/psp_main.c
@@ -300,6 +300,9 @@ int psp_dev_rcv(struct sk_buff *skb, u16 dev_id, u8 generation, bool strip_icv)
 	if (proto == htons(ETH_P_IP)) {
 		struct iphdr *iph = (struct iphdr *)(skb->data + l2_hlen);
 
+		if (unlikely(iph->ihl < 5))
+			return -EINVAL;
+
 		is_udp = iph->protocol == IPPROTO_UDP;
 		l3_hlen = iph->ihl * 4;
 		if (l3_hlen != sizeof(struct iphdr) &&
@@ -335,6 +338,9 @@ int psp_dev_rcv(struct sk_buff *skb, u16 dev_id, u8 generation, bool strip_icv)
 	if (proto == htons(ETH_P_IP)) {
 		struct iphdr *iph = (struct iphdr *)(skb->data + l2_hlen);
 
+		if (unlikely(ntohs(iph->tot_len) < l3_hlen + encap))
+			return -EINVAL;
+
 		iph->protocol = psph->nexthdr;
 		iph->tot_len = htons(ntohs(iph->tot_len) - encap);
 		iph->check = 0;
@@ -342,6 +348,9 @@ int psp_dev_rcv(struct sk_buff *skb, u16 dev_id, u8 generation, bool strip_icv)
 	} else {
 		struct ipv6hdr *ipv6h = (struct ipv6hdr *)(skb->data + l2_hlen);
 
+		if (unlikely(ntohs(ipv6h->payload_len) < encap))
+			return -EINVAL;
+
 		ipv6h->nexthdr = psph->nexthdr;
 		ipv6h->payload_len = htons(ntohs(ipv6h->payload_len) - encap);
 	}
-- 
2.54.0