netdev - [PATCH net-next] seg6: fix parameter passing when calling NF

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Message-ID: <2a78f16a-0ff5-46bf-983b-9ab038f5a5cd@163.com>
Date: Thu, 30 May 2024 15:43:38 +0800
From: Jianguo Wu <wujianguo106@....com>
To: netdev <netdev@...r.kernel.org>
Cc: contact@...elbtn.com, pablo@...filter.org,
 David Ahern <dsahern@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Subject: [PATCH net-next] seg6: fix parameter passing when calling NF_HOOK()
 in End.DX4 and End.DX6 behaviors

From: Jianguo Wu <wujianguo@...natelecom.cn>

input_action_end_dx4() and input_action_end_dx6() call NF_HOOK() for PREROUTING hook,
for PREROUTING hook, we should passing a valid indev, and a NULL outdev to NF_HOOK(),
otherwise may trigger a NULL pointer dereference, as below:

    [74830.647293] BUG: kernel NULL pointer dereference, address: 0000000000000090
    [74830.655633] #PF: supervisor read access in kernel mode
    [74830.657888] #PF: error_code(0x0000) - not-present page
    [74830.659500] PGD 0 P4D 0
    [74830.660450] Oops: 0000 [#1] PREEMPT SMP PTI
    ...
    [74830.664953] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
    [74830.666569] RIP: 0010:rpfilter_mt+0x44/0x15e [ipt_rpfilter]
    ...
    [74830.689725] Call Trace:
    [74830.690402]  <IRQ>
    [74830.690953]  ? show_trace_log_lvl+0x1c4/0x2df
    [74830.692020]  ? show_trace_log_lvl+0x1c4/0x2df
    [74830.693095]  ? ipt_do_table+0x286/0x710 [ip_tables]
    [74830.694275]  ? __die_body.cold+0x8/0xd
    [74830.695205]  ? page_fault_oops+0xac/0x140
    [74830.696244]  ? exc_page_fault+0x62/0x150
    [74830.697225]  ? asm_exc_page_fault+0x22/0x30
    [74830.698344]  ? rpfilter_mt+0x44/0x15e [ipt_rpfilter]
    [74830.699540]  ipt_do_table+0x286/0x710 [ip_tables]
    [74830.700758]  ? ip6_route_input+0x19d/0x240
    [74830.701752]  nf_hook_slow+0x3f/0xb0
    [74830.702678]  input_action_end_dx4+0x19b/0x1e0
    [74830.703735]  ? input_action_end_t+0xe0/0xe0
    [74830.704734]  seg6_local_input_core+0x2d/0x60
    [74830.705782]  lwtunnel_input+0x5b/0xb0
    [74830.706690]  __netif_receive_skb_one_core+0x63/0xa0
    [74830.707825]  process_backlog+0x99/0x140
    [74830.709538]  __napi_poll+0x2c/0x160
    [74830.710673]  net_rx_action+0x296/0x350
    [74830.711860]  __do_softirq+0xcb/0x2ac
    [74830.713049]  do_softirq+0x63/0x90

input_action_end_dx4() passing a NULL indev to NF_HOOK(), and finally trigger a
NULL dereference in rpfilter_mt()->rpfilter_is_loopback():
    static bool
    rpfilter_is_loopback(const struct sk_buff *skb, const struct net_device *in)
    {
            // in is NULL
            return skb->pkt_type == PACKET_LOOPBACK || in->flags & IFF_LOOPBACK;
    }

Fixes: 7a3f5b0de364 ("netfilter: add netfilter hooks to SRv6 data plane")

Signed-off-by: Jianguo Wu <wujianguo@...natelecom.cn>
---
 net/ipv6/seg6_local.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/seg6_local.c b/net/ipv6/seg6_local.c
index 24e2b4b..c434940 100644
--- a/net/ipv6/seg6_local.c
+++ b/net/ipv6/seg6_local.c
@@ -941,8 +941,8 @@ static int input_action_end_dx6(struct sk_buff *skb,

 	if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
 		return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,
-			       dev_net(skb->dev), NULL, skb, NULL,
-			       skb_dst(skb)->dev, input_action_end_dx6_finish);
+			       dev_net(skb->dev), NULL, skb, skb->dev,
+			       NULL, input_action_end_dx6_finish);

 	return input_action_end_dx6_finish(dev_net(skb->dev), NULL, skb);
 drop:
@@ -991,8 +991,8 @@ static int input_action_end_dx4(struct sk_buff *skb,

 	if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
 		return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,
-			       dev_net(skb->dev), NULL, skb, NULL,
-			       skb_dst(skb)->dev, input_action_end_dx4_finish);
+			       dev_net(skb->dev), NULL, skb, skb->dev,
+			       NULL, input_action_end_dx4_finish);

 	return input_action_end_dx4_finish(dev_net(skb->dev), NULL, skb);
 drop:
-- 
1.8.3.1