From: Sun Jian <sun.jian.kdev@gmail.com>
Date: Wed, 8 Apr 2026 03:46:22 +0000 (+0800)
Subject: bpf: reject short IPv4/IPv6 inputs in bpf_prog_test_run_skb
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=12bec2bd4b76d81c5d3996bd14ec1b7f4d983747;p=thirdparty%2Fkernel%2Flinux.git

bpf: reject short IPv4/IPv6 inputs in bpf_prog_test_run_skb

bpf_prog_test_run_skb() calls eth_type_trans() first and then uses
skb->protocol to initialize sk family and address fields for the test
run.

For IPv4 and IPv6 packets, it may access ip_hdr(skb) or ipv6_hdr(skb)
even when the provided test input only contains an Ethernet header.

Reject the input earlier if the Ethernet frame carries IPv4/IPv6
EtherType but the L3 header is too short.

Fold the IPv4/IPv6 header length checks into the existing protocol
switch and return -EINVAL before accessing the network headers.

Fixes: fa5cb548ced6 ("bpf: Setup socket family and addresses in bpf_prog_test_run_skb")
Reported-by: syzbot+619b9ef527f510a57cfc@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=619b9ef527f510a57cfc
Signed-off-by: Sun Jian <sun.jian.kdev@gmail.com>
Link: https://lore.kernel.org/r/20260408034623.180320-2-sun.jian.kdev@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 4cd6b3ea1815a..2bc04feadfabe 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -1137,19 +1137,23 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
 
 	switch (skb->protocol) {
 	case htons(ETH_P_IP):
-		sk->sk_family = AF_INET;
-		if (sizeof(struct iphdr) <= skb_headlen(skb)) {
-			sk->sk_rcv_saddr = ip_hdr(skb)->saddr;
-			sk->sk_daddr = ip_hdr(skb)->daddr;
+		if (skb_headlen(skb) < sizeof(struct iphdr)) {
+			ret = -EINVAL;
+			goto out;
 		}
+		sk->sk_family = AF_INET;
+		sk->sk_rcv_saddr = ip_hdr(skb)->saddr;
+		sk->sk_daddr = ip_hdr(skb)->daddr;
 		break;
 #if IS_ENABLED(CONFIG_IPV6)
 	case htons(ETH_P_IPV6):
-		sk->sk_family = AF_INET6;
-		if (sizeof(struct ipv6hdr) <= skb_headlen(skb)) {
-			sk->sk_v6_rcv_saddr = ipv6_hdr(skb)->saddr;
-			sk->sk_v6_daddr = ipv6_hdr(skb)->daddr;
+		if (skb_headlen(skb) < sizeof(struct ipv6hdr)) {
+			ret = -EINVAL;
+			goto out;
 		}
+		sk->sk_family = AF_INET6;
+		sk->sk_v6_rcv_saddr = ipv6_hdr(skb)->saddr;
+		sk->sk_v6_daddr = ipv6_hdr(skb)->daddr;
 		break;
 #endif
 	default: