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Message-Id: <20240117234304.1250-1-hdanton@sina.com>
Date: Thu, 18 Jan 2024 07:43:04 +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/core/flow_dissector.c
+++ y/net/core/flow_dissector.c
@@ -1164,9 +1164,11 @@ proto_again:
switch (proto) {
case htons(ETH_P_IP): {
const struct iphdr *iph;
- struct iphdr _iph;
- iph = __skb_header_pointer(skb, nhoff, sizeof(_iph), data, hlen, &_iph);
+ if (pskb_network_may_pull(skb, sizeof(struct iphdr)))
+ iph = (void *) skb_network_header(skb);
+ else
+ iph = NULL;
if (!iph || iph->ihl < 5) {
fdret = FLOW_DISSECT_RET_OUT_BAD;
break;
--- x/net/netfilter/nf_conntrack_core.c
+++ y/net/netfilter/nf_conntrack_core.c
@@ -346,9 +346,11 @@ static int ipv4_get_l4proto(const struct
{
int dataoff = -1;
const struct iphdr *iph;
- struct iphdr _iph;
- iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
+ if (pskb_network_may_pull(skb, sizeof(struct iphdr)))
+ iph = (void *) skb_network_header(skb);
+ else
+ iph = NULL;
if (!iph)
return -1;
--
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