netdev - [PATCH net] bonding: fix oops during rmmod

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <641f914f-3216-4eeb-87dd-91b78aa97773@cybernetics.com>
Date: Tue, 14 May 2024 15:57:29 -0400
From: Tony Battersby <tonyb@...ernetics.com>
To: "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>
Cc: Jay Vosburgh <j.vosburgh@...il.com>, Andy Gospodarek
 <andy@...yhouse.net>, Zhengchao Shao <shaozhengchao@...wei.com>,
 netdev@...r.kernel.org
Subject: [PATCH net] bonding: fix oops during rmmod

"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@...r.kernel.org
Signed-off-by: Tony Battersby <tonyb@...ernetics.com>
---
 drivers/net/bonding/bond_main.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 2c5ed0a7cb18..bceda85f0dcf 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -6477,16 +6477,16 @@ 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)
@@ -6501,10 +6501,11 @@ 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;
 
 }
@@ -6513,11 +6514,11 @@ 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));

base-commit: a38297e3fb012ddfa7ce0321a7e5a8daeb1872b6
-- 
2.25.1