Subject: [PATCH net v3 03/11] bonding: fix unexpected IFF_BONDING bit unset

From: Taehee Yoo <[email-masked]>
Date: Mon, 16 Sep 2019 22:47:54 +0900

The IFF_BONDING means bonding master or bonding slave device.
->ndo_add_slave() sets IFF_BONDING flag and ->ndo_del_slave() unsets
IFF_BONDING flag.

bond0<--bond1

Both bond0 and bond1 are bonding device and these should keep having
IFF_BONDING flag until they are removed.
But bond1 would lose IFF_BONDING at ->ndo_del_slave() because that routine
do not check whether the slave device is the bonding type or not.
This patch adds the interface type check routine before removing
IFF_BONDING flag.

Test commands:
    ip link add bond0 type bond
    ip link add bond1 type bond
    ip link set bond1 master bond0
    ip link set bond1 nomaster
    ip link del bond1 type bond
    ip link add bond1 type bond

Splat looks like:
[   58.210981] proc_dir_entry 'bonding/bond1' already registered
[   58.463875] WARNING: CPU: 0 PID: 955 at fs/proc/generic.c:361 proc_register+0x2a9/0x3e0
[   58.466423] Modules linked in: bonding veth openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipv6 nfs
[   58.483855] CPU: 0 PID: 955 Comm: ip Not tainted 5.3.0-rc8+ #179
[   58.484657] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
[   58.485779] RIP: 0010:proc_register+0x2a9/0x3e0
[   58.486377] Code: 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 39 01 00 00 48 8b 04 24 48 89 ea 48 c7 c7 60 0f 14 bd 480
[   58.489003] RSP: 0018:ffff8880cc007078 EFLAGS: 00010282
[   58.553743] RAX: dffffc0000000008 RBX: ffff8880ce23c0d0 RCX: ffffffffbbd021e2
[   58.584076] RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffff8880da5f6b8c
[   58.584901] RBP: ffff8880ce23c353 R08: ffffed101b4bff91 R09: ffffed101b4bff91
[   58.585724] R10: 0000000000000001 R11: ffffed101b4bff90 R12: ffff8880ce23c268
[   58.586508] R13: ffff8880ce23c352 R14: dffffc0000000000 R15: ffffed1019c4786a
[   58.587296] FS:  00007f52d53b60c0(0000) GS:ffff8880da400000(0000) knlGS:0000000000000000
[   58.588247] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   58.653694] CR2: 00007f31a9df9320 CR3: 00000000cd4ea006 CR4: 00000000000606f0
[   58.654591] Call Trace:
[   58.654895]  proc_create_seq_private+0xb3/0xf0
[   58.655400]  bond_create_proc_entry+0x1b3/0x3f0 [bonding]
[   58.655985]  bond_netdev_event+0x433/0x970 [bonding]
[   58.656545]  ? __module_text_address+0x13/0x140
[   58.657038]  notifier_call_chain+0x90/0x160
[   58.657541]  register_netdevice+0x9b3/0xd80
[   58.657999]  ? alloc_netdev_mqs+0x854/0xc10
[   58.658476]  ? netdev_change_features+0xa0/0xa0
[   58.663592]  ? rtnl_create_link+0x2ed/0xad0
[   58.664049]  bond_newlink+0x2a/0x60 [bonding]
[   58.664529]  __rtnl_newlink+0xb9f/0x11b0
[   58.665014]  ? rtnl_link_unregister+0x230/0x230
[ ... ]

Fixes: 0b680e753724 ("[PATCH] bonding: Add priv_flag to avoid event mishandling")
Signed-off-by: Taehee Yoo <[email-masked]>
---

v2 -> v3 :
 - This patch is not changed
v1 -> v2 :
 - Do not add a new priv_flag.

 drivers/net/bonding/bond_main.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 931d9d935686..0db12fcfc953 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1816,7 +1816,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev,
 	slave_disable_netpoll(new_slave);
 
 err_close:
-	slave_dev->priv_flags &= ~IFF_BONDING;
+	if (!netif_is_bond_master(slave_dev))
+		slave_dev->priv_flags &= ~IFF_BONDING;
 	dev_close(slave_dev);
 
 err_restore_mac:
@@ -2017,7 +2018,8 @@ static int __bond_release_one(struct net_device *bond_dev,
 	else
 		dev_set_mtu(slave_dev, slave->original_mtu);
 
-	slave_dev->priv_flags &= ~IFF_BONDING;
+	if (!netif_is_bond_master(slave_dev))
+		slave_dev->priv_flags &= ~IFF_BONDING;
 
 	bond_free_slave(slave);
 
-- 
2.17.1