From: Kyle Zeng <zengyhkyle@gmail.com>
Date: Thu, 14 Sep 2023 22:12:57 -0700
Subject: ipv4: fix null-deref in ipv4_link_failure
Patch-mainline: v6.6-rc3
Git-commit: 0113d9c9d1ccc07f5a3710dac4aa24b6d711278c
References: CVE-2023-42754 bsc#1215467
Currently, we assume the skb is associated with a device before calling
__ip_options_compile, which is not always the case if it is re-routed by
ipvs.
When skb->dev is NULL, dev_net(skb->dev) will become null-dereference.
This patch adds a check for the edge case and switch to use the net_device
from the rtable when skb->dev is NULL.
Fixes: ed0de45a1008 ("ipv4: recompile ip options in ipv4_link_failure")
Suggested-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Kyle Zeng <zengyhkyle@gmail.com>
Cc: Stephen Suryaputra <ssuryaextr@gmail.com>
Cc: Vadim Fedorenko <vfedorenko@novek.ru>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Michal Kubecek <mkubecek@suse.cz>
---
net/ipv4/route.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1217,6 +1217,7 @@ static struct dst_entry *ipv4_dst_check(struct dst_entry *dst, u32 cookie)
static void ipv4_send_dest_unreach(struct sk_buff *skb)
{
+ struct net_device *dev;
struct ip_options opt;
int res;
@@ -1234,7 +1235,8 @@ static void ipv4_send_dest_unreach(struct sk_buff *skb)
opt.optlen = ip_hdr(skb)->ihl * 4 - sizeof(struct iphdr);
rcu_read_lock();
- res = __ip_options_compile(dev_net(skb->dev), &opt, skb, NULL);
+ dev = skb->dev ? skb->dev : skb_rtable(skb)->dst.dev;
+ res = __ip_options_compile(dev_net(dev), &opt, skb, NULL);
rcu_read_unlock();
if (res)