Re: [syzbot] [net?] KASAN: use-after-free Read in __skb_flow_dissect (3)

[Hillf Danton]

On Mon, 01 Jan 2024 09:18:16 -0800
> syzbot found the following issue on:
> 
> HEAD commit:    f5837722ffec Merge tag 'mm-hotfixes-stable-2023-12-27-15-0..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=122dfc65e80000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  master

--- x/net/ipv4/ipip.c
+++ y/net/ipv4/ipip.c
@@ -277,8 +277,9 @@ static netdev_tx_t ipip_tunnel_xmit(stru
 	struct ip_tunnel *tunnel = netdev_priv(dev);
 	const struct iphdr  *tiph = &tunnel->parms.iph;
 	u8 ipproto;
+	int pull_len = tunnel->hlen + sizeof(struct iphdr);
 
-	if (!pskb_inet_may_pull(skb))
+	if (!pskb_network_may_pull(skb, pull_len))
 		goto tx_error;
 
 	switch (skb->protocol) {
--