6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tony Battersby <tonyb@xxxxxxxxxxxxxxx>
commit a45835a0bb6ef7d5ddbc0714dd760de979cb6ece upstream.
"rmmod bonding" causes an oops ever since commit cc317ea3d927 ("bonding:
remove redundant NULL check in debugfs function"). Here are the relevant
functions being called:
bonding_exit()
bond_destroy_debugfs()
debugfs_remove_recursive(bonding_debug_root);
bonding_debug_root = NULL; <--------- SET TO NULL HERE
bond_netlink_fini()
rtnl_link_unregister()
__rtnl_link_unregister()
unregister_netdevice_many_notify()
bond_uninit()
bond_debug_unregister()
(commit removed check for bonding_debug_root == NULL)
debugfs_remove()
simple_recursive_removal()
down_write() -> OOPS
However, reverting the bad commit does not solve the problem completely
because the original code contains a race that could cause the same
oops, although it was much less likely to be triggered unintentionally:
CPU1
rmmod bonding
bonding_exit()
bond_destroy_debugfs()
debugfs_remove_recursive(bonding_debug_root);
CPU2
echo -bond0 > /sys/class/net/bonding_masters
bond_uninit()
bond_debug_unregister()
if (!bonding_debug_root)
CPU1
bonding_debug_root = NULL;
So do NOT revert the bad commit (since the removed checks were racy
anyway), and instead change the order of actions taken during module
removal. The same oops can also happen if there is an error during
module init, so apply the same fix there.
Fixes: cc317ea3d927 ("bonding: remove redundant NULL check in debugfs function")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Tony Battersby <tonyb@xxxxxxxxxxxxxxx>
Reviewed-by: Simon Horman <horms@xxxxxxxxxx>
Acked-by: Jay Vosburgh <jay.vosburgh@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/641f914f-3216-4eeb-87dd-91b78aa97773@xxxxxxxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/bonding/bond_main.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -6484,16 +6484,16 @@ static int __init bonding_init(void)
if (res)
goto out;
+ bond_create_debugfs();
+
res = register_pernet_subsys(&bond_net_ops);
if (res)
- goto out;
+ goto err_net_ops;
res = bond_netlink_init();
if (res)
goto err_link;
- bond_create_debugfs();
-
for (i = 0; i < max_bonds; i++) {
res = bond_create(&init_net, NULL);
if (res)
@@ -6508,10 +6508,11 @@ static int __init bonding_init(void)
out:
return res;
err:
- bond_destroy_debugfs();
bond_netlink_fini();
err_link:
unregister_pernet_subsys(&bond_net_ops);
+err_net_ops:
+ bond_destroy_debugfs();
goto out;
}
@@ -6520,11 +6521,11 @@ static void __exit bonding_exit(void)
{
unregister_netdevice_notifier(&bond_netdev_notifier);
- bond_destroy_debugfs();
-
bond_netlink_fini();
unregister_pernet_subsys(&bond_net_ops);
+ bond_destroy_debugfs();
+
#ifdef CONFIG_NET_POLL_CONTROLLER
/* Make sure we don't have an imbalance on our netpoll blocking */
WARN_ON(atomic_read(&netpoll_block_tx));
