[PATCH] bonding: fix devconf_all NULL dereference when IPv6 is disabled

[zhangzl2013@126.com]

From: Zhaolong Zhang <zhangzl68@chinatelecom.cn>

When booting with the 'ipv6.disable=1' parameter, the devconf_all is
never initialized because inet6_init() exits before addrconf_init() is
called which initializes it. bond_send_validate(), however, will still
call bond_ns_send_all() even ipv6 is indeed disabled. It will lead to
NULL derefence of net->ipv6.devconf_all in ip6_pol_route().

 BUG: kernel NULL pointer dereference, address: 000000000000000c
 [...]
 Workqueue: bond0 bond_arp_monitor [bonding]
 RIP: 0010:ip6_pol_route+0x69/0x480
 [...]
 Call Trace:
  <TASK>
  ? srso_return_thunk+0x5/0x5f
  ? __pfx_ip6_pol_route_output+0x10/0x10
  fib6_rule_lookup+0xfe/0x260
  ? wakeup_preempt+0x8a/0x90
  ? srso_return_thunk+0x5/0x5f
  ? srso_return_thunk+0x5/0x5f
  ? sched_balance_rq+0x369/0x810
  ip6_route_output_flags+0xd7/0x170
  bond_ns_send_all+0xde/0x280 [bonding]
  bond_ab_arp_probe+0x296/0x320 [bonding]
  ? srso_return_thunk+0x5/0x5f
  bond_activebackup_arp_mon+0xb4/0x2c0 [bonding]
  process_one_work+0x196/0x370
  worker_thread+0x1af/0x320
  ? srso_return_thunk+0x5/0x5f
  ? __pfx_worker_thread+0x10/0x10
  kthread+0xe3/0x120
  ? __pfx_kthread+0x10/0x10
  ret_from_fork+0x199/0x260
  ? __pfx_kthread+0x10/0x10
  ret_from_fork_asm+0x1a/0x30
  </TASK>

Fix this by adding ipv6_mod_enabled() condition check in the caller.

Fixes: 4e24be018eb9 ("bonding: add new parameter ns_targets")
Signed-off-by: Qianheng Peng <pengqh1@chinatelecom.cn>
Signed-off-by: Zhaolong Zhang <zhangzl68@chinatelecom.cn>
---
 drivers/net/bonding/bond_main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index e044fc733b8c..522eab060f9e 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3455,7 +3455,8 @@ static void bond_send_validate(struct bonding *bond, struct slave *slave)
 {
 	bond_arp_send_all(bond, slave);
 #if IS_ENABLED(CONFIG_IPV6)
-	bond_ns_send_all(bond, slave);
+	if (likely(ipv6_mod_enabled()))
+		bond_ns_send_all(bond, slave);
 #endif
 }
 
-- 
2.52.0