[PATCH net 3/3] net: bonding: Fix nd_tbl NULL dereference when IPv6 is disabled

["Ricardo B. Marlière" <rbm@suse.com>]

When booting with the 'ipv6.disable=1' parameter, the nd_tbl is never
initialized because inet6_init() exits before ndisc_init() is called
which initializes it. If bonding ARP/NS validation is enabled, an IPv6
NS/NA packet received on a slave can reach bond_validate_na(), which
calls bond_has_this_ip6(). That path calls ipv6_chk_addr() and can
crash in __ipv6_chk_addr_and_flags().

 BUG: kernel NULL pointer dereference, address: 00000000000005d8
 Oops: Oops: 0000 [#1] SMP NOPTI
 RIP: 0010:__ipv6_chk_addr_and_flags+0x69/0x170
 Call Trace:
  <IRQ>
  ipv6_chk_addr+0x1f/0x30
  bond_validate_na+0x12e/0x1d0 [bonding]
  ? __pfx_bond_handle_frame+0x10/0x10 [bonding]
  bond_rcv_validate+0x1a0/0x450 [bonding]
  bond_handle_frame+0x5e/0x290 [bonding]
  ? srso_alias_return_thunk+0x5/0xfbef5
  __netif_receive_skb_core.constprop.0+0x3e8/0xe50
  ? srso_alias_return_thunk+0x5/0xfbef5
  ? update_cfs_rq_load_avg+0x1a/0x240
  ? srso_alias_return_thunk+0x5/0xfbef5
  ? __enqueue_entity+0x5e/0x240
  __netif_receive_skb_one_core+0x39/0xa0
  process_backlog+0x9c/0x150
  __napi_poll+0x30/0x200
  ? srso_alias_return_thunk+0x5/0xfbef5
  net_rx_action+0x338/0x3b0
  handle_softirqs+0xc9/0x2a0
  do_softirq+0x42/0x60
  </IRQ>
  <TASK>
  __local_bh_enable_ip+0x62/0x70
  __dev_queue_xmit+0x2d3/0x1000
  ? srso_alias_return_thunk+0x5/0xfbef5
  ? srso_alias_return_thunk+0x5/0xfbef5
  ? packet_parse_headers+0x10a/0x1a0
  packet_sendmsg+0x10da/0x1700
  ? kick_pool+0x5f/0x140
  ? srso_alias_return_thunk+0x5/0xfbef5
  ? __queue_work+0x12d/0x4f0
  __sys_sendto+0x1f3/0x220
  __x64_sys_sendto+0x24/0x30
  do_syscall_64+0x101/0xf80
  ? exc_page_fault+0x6e/0x170
  ? srso_alias_return_thunk+0x5/0xfbef5
  entry_SYSCALL_64_after_hwframe+0x77/0x7f
  </TASK>

Fix this by adding an early check in bond_confirm_addr6(). If
ipv6_stub->nd_tbl is NULL, return before calling ipv6_chk_addr().

Suggested-by: Fernando Fernandez Mancera <fmancera@suse.de>
Fixes: 4e24be018eb9 ("bonding: add new parameter ns_targets")
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
---
 drivers/net/bonding/bond_main.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index a1de08ee3815..013d037b644a 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -90,6 +90,7 @@
 #include <net/tls.h>
 #endif
 #include <net/ip6_route.h>
+#include <net/ipv6_stubs.h>
 #include <net/netdev_lock.h>
 #include <net/xdp.h>
 
@@ -3251,6 +3252,9 @@ static int bond_confirm_addr6(struct net_device *dev,
 {
 	struct in6_addr *addr = (struct in6_addr *)priv->data;
 
+	if (!ipv6_stub->nd_tbl)
+		return 0;
+
 	return ipv6_chk_addr(dev_net(dev), addr, dev, 0);
 }
 

-- 
2.53.0