linux-kernel - Re: [syzbot] [net?] KASAN: use-after-free Read in __skb_flow

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Message-Id: <20240117112318.1038-1-hdanton@sina.com>
Date: Wed, 17 Jan 2024 19:23:18 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+bfde3bef047a81b8fde6@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] KASAN: use-after-free Read in __skb_flow_dissect (3)

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) {
--