[PATCH net] ipvlan: Fix out-of-bound bugs caused by unset skb->mac_header

* [PATCH net] ipvlan: Fix out-of-bound bugs caused by unset skb->mac_header
@ 2022-09-07 10:12 Lu Wei
  2022-09-07 16:18 ` Eric Dumazet
  2022-09-09 11:50 ` patchwork-bot+netdevbpf
  0 siblings, 2 replies; 3+ messages in thread
From: Lu Wei @ 2022-09-07 10:12 UTC (permalink / raw)
  To: davem, edumazet, kuba, pabeni, vulab, maheshb, netdev; +Cc: linux-kernel

If an AF_PACKET socket is used to send packets through ipvlan and the
default xmit function of the AF_PACKET socket is changed from
dev_queue_xmit() to packet_direct_xmit() via setsockopt() with the option
name of PACKET_QDISC_BYPASS, the skb->mac_header may not be reset and
remains as the initial value of 65535, this may trigger slab-out-of-bounds
bugs as following:

=================================================================
UG: KASAN: slab-out-of-bounds in ipvlan_xmit_mode_l2+0xdb/0x330 [ipvlan]
PU: 2 PID: 1768 Comm: raw_send Kdump: loaded Not tainted 6.0.0-rc4+ #6
ardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33
all Trace:
print_address_description.constprop.0+0x1d/0x160
print_report.cold+0x4f/0x112
kasan_report+0xa3/0x130
ipvlan_xmit_mode_l2+0xdb/0x330 [ipvlan]
ipvlan_start_xmit+0x29/0xa0 [ipvlan]
__dev_direct_xmit+0x2e2/0x380
packet_direct_xmit+0x22/0x60
packet_snd+0x7c9/0xc40
sock_sendmsg+0x9a/0xa0
__sys_sendto+0x18a/0x230
__x64_sys_sendto+0x74/0x90
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd

The root cause is:
  1. packet_snd() only reset skb->mac_header when sock->type is SOCK_RAW
     and skb->protocol is not specified as in packet_parse_headers()

  2. packet_direct_xmit() doesn't reset skb->mac_header as dev_queue_xmit()

In this case, skb->mac_header is 65535 when ipvlan_xmit_mode_l2() is
called. So when ipvlan_xmit_mode_l2() gets mac header with eth_hdr() which
use "skb->head + skb->mac_header", out-of-bound access occurs.

This patch replaces eth_hdr() with skb_eth_hdr() in ipvlan_xmit_mode_l2()
and reset mac header in multicast to solve this out-of-bound bug.

Fixes: 2ad7bf363841 ("ipvlan: Initial check-in of the IPVLAN driver.")
Signed-off-by: Lu Wei <luwei32@huawei.com>
---
 drivers/net/ipvlan/ipvlan_core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ipvlan/ipvlan_core.c b/drivers/net/ipvlan/ipvlan_core.c
index dfeb5b392e64..bb1c298c1e78 100644
--- a/drivers/net/ipvlan/ipvlan_core.c
+++ b/drivers/net/ipvlan/ipvlan_core.c
@@ -495,7 +495,6 @@ static int ipvlan_process_v6_outbound(struct sk_buff *skb)
 
 static int ipvlan_process_outbound(struct sk_buff *skb)
 {
-	struct ethhdr *ethh = eth_hdr(skb);
 	int ret = NET_XMIT_DROP;
 
 	/* The ipvlan is a pseudo-L2 device, so the packets that we receive
@@ -505,6 +504,8 @@ static int ipvlan_process_outbound(struct sk_buff *skb)
 	if (skb_mac_header_was_set(skb)) {
 		/* In this mode we dont care about
 		 * multicast and broadcast traffic */
+		struct ethhdr *ethh = eth_hdr(skb);
+
 		if (is_multicast_ether_addr(ethh->h_dest)) {
 			pr_debug_ratelimited(
 				"Dropped {multi|broad}cast of type=[%x]\n",
@@ -589,7 +590,7 @@ static int ipvlan_xmit_mode_l3(struct sk_buff *skb, struct net_device *dev)
 static int ipvlan_xmit_mode_l2(struct sk_buff *skb, struct net_device *dev)
 {
 	const struct ipvl_dev *ipvlan = netdev_priv(dev);
-	struct ethhdr *eth = eth_hdr(skb);
+	struct ethhdr *eth = skb_eth_hdr(skb);
 	struct ipvl_addr *addr;
 	void *lyr3h;
 	int addr_type;
@@ -619,6 +620,7 @@ static int ipvlan_xmit_mode_l2(struct sk_buff *skb, struct net_device *dev)
 		return dev_forward_skb(ipvlan->phy_dev, skb);
 
 	} else if (is_multicast_ether_addr(eth->h_dest)) {
+		skb_reset_mac_header(skb);
 		ipvlan_skb_crossing_ns(skb, NULL);
 		ipvlan_multicast_enqueue(ipvlan->port, skb, true);
 		return NET_XMIT_SUCCESS;
-- 
2.31.1


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