Subject: Re: [BUG] kmemleak in rtnetlink_rcv() triggered by selftests/drivers/net/team in build cdc9718d5e59

From: Ido Schimmel <[email-masked]>
Date: Sun, 9 Apr 2023 20:14:13 +0300

On Sun, Apr 09, 2023 at 01:49:30PM +0200, Mirsad Goran Todorovac wrote:
> Hi all,
> 
> There appears to be a memleak triggered by the selftest drivers/net/team.

Thanks for the report. Not sure it's related to team, see below.

> 
> # cat /sys/kernel/debug/kmemleak
> unreferenced object 0xffff8c18def8ee00 (size 256):
>   comm "ip", pid 5727, jiffies 4294961159 (age 954.244s)
>   hex dump (first 32 bytes):
>     00 20 09 de 18 8c ff ff 00 00 00 00 00 00 00 00  . ..............
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffffb60fb25c>] slab_post_alloc_hook+0x8c/0x3e0
>     [<ffffffffb6102b39>] __kmem_cache_alloc_node+0x1d9/0x2a0
>     [<ffffffffb607684e>] kmalloc_trace+0x2e/0xc0
>     [<ffffffffb6dbc00b>] vlan_vid_add+0x11b/0x290
>     [<ffffffffb6dbcffc>] vlan_device_event+0x19c/0x880
>     [<ffffffffb5dde4d7>] raw_notifier_call_chain+0x47/0x70
>     [<ffffffffb6ab6940>] call_netdevice_notifiers_info+0x50/0xa0
>     [<ffffffffb6ac7574>] dev_open+0x94/0xa0
>     [<ffffffffc176515e>] 0xffffffffc176515e

Don't know what this is. Might be another issue.

>     [<ffffffffb6ada6b0>] do_set_master+0x90/0xb0
>     [<ffffffffb6adc5f4>] do_setlink+0x514/0x11f0
>     [<ffffffffb6ae4507>] __rtnl_newlink+0x4e7/0xa10
>     [<ffffffffb6ae4a8c>] rtnl_newlink+0x4c/0x70
>     [<ffffffffb6adf334>] rtnetlink_rcv_msg+0x184/0x5d0
>     [<ffffffffb6b6ad1e>] netlink_rcv_skb+0x5e/0x110
>     [<ffffffffb6ada0e9>] rtnetlink_rcv+0x19/0x20
> unreferenced object 0xffff8c18250d3700 (size 32):
>   comm "ip", pid 5727, jiffies 4294961159 (age 954.244s)
>   hex dump (first 32 bytes):
>     a0 ee f8 de 18 8c ff ff a0 ee f8 de 18 8c ff ff  ................
>     81 00 00 00 01 00 00 00 cc cc cc cc cc cc cc cc  ................
>   backtrace:
>     [<ffffffffb60fb25c>] slab_post_alloc_hook+0x8c/0x3e0
>     [<ffffffffb6102b39>] __kmem_cache_alloc_node+0x1d9/0x2a0
>     [<ffffffffb607684e>] kmalloc_trace+0x2e/0xc0
>     [<ffffffffb6dbc064>] vlan_vid_add+0x174/0x290
>     [<ffffffffb6dbcffc>] vlan_device_event+0x19c/0x880
>     [<ffffffffb5dde4d7>] raw_notifier_call_chain+0x47/0x70
>     [<ffffffffb6ab6940>] call_netdevice_notifiers_info+0x50/0xa0
>     [<ffffffffb6ac7574>] dev_open+0x94/0xa0
>     [<ffffffffc176515e>] 0xffffffffc176515e
>     [<ffffffffb6ada6b0>] do_set_master+0x90/0xb0
>     [<ffffffffb6adc5f4>] do_setlink+0x514/0x11f0
>     [<ffffffffb6ae4507>] __rtnl_newlink+0x4e7/0xa10
>     [<ffffffffb6ae4a8c>] rtnl_newlink+0x4c/0x70
>     [<ffffffffb6adf334>] rtnetlink_rcv_msg+0x184/0x5d0
>     [<ffffffffb6b6ad1e>] netlink_rcv_skb+0x5e/0x110
>     [<ffffffffb6ada0e9>] rtnetlink_rcv+0x19/0x20
> unreferenced object 0xffff8c1846e16800 (size 256):
>   comm "ip", pid 7837, jiffies 4295135225 (age 258.160s)
>   hex dump (first 32 bytes):
>     00 20 f7 de 18 8c ff ff 00 00 00 00 00 00 00 00  . ..............
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffffb60fb25c>] slab_post_alloc_hook+0x8c/0x3e0
>     [<ffffffffb6102b39>] __kmem_cache_alloc_node+0x1d9/0x2a0
>     [<ffffffffb607684e>] kmalloc_trace+0x2e/0xc0
>     [<ffffffffb6dbc00b>] vlan_vid_add+0x11b/0x290
>     [<ffffffffb6dbcffc>] vlan_device_event+0x19c/0x880
>     [<ffffffffb5dde4d7>] raw_notifier_call_chain+0x47/0x70
>     [<ffffffffb6ab6940>] call_netdevice_notifiers_info+0x50/0xa0
>     [<ffffffffb6ac7574>] dev_open+0x94/0xa0
>     [<ffffffffc177115e>] bond_enslave+0x34e/0x1840 [bonding]

This shows that the issue is related to the bond driver, not team.

>     [<ffffffffb6ada6b0>] do_set_master+0x90/0xb0
>     [<ffffffffb6adc5f4>] do_setlink+0x514/0x11f0
>     [<ffffffffb6ae4507>] __rtnl_newlink+0x4e7/0xa10
>     [<ffffffffb6ae4a8c>] rtnl_newlink+0x4c/0x70
>     [<ffffffffb6adf334>] rtnetlink_rcv_msg+0x184/0x5d0
>     [<ffffffffb6b6ad1e>] netlink_rcv_skb+0x5e/0x110
>     [<ffffffffb6ada0e9>] rtnetlink_rcv+0x19/0x20
> unreferenced object 0xffff8c184c5ff2a0 (size 32):

This is 'struct vlan_vid_info'

>   comm "ip", pid 7837, jiffies 4295135225 (age 258.160s)
>   hex dump (first 32 bytes):
>     a0 68 e1 46 18 8c ff ff a0 68 e1 46 18 8c ff ff  .h.F.....h.F....
>     81 00 00 00 01 00 00 00 cc cc cc cc cc cc cc cc  ................
            ^ VLAN ID 0

>   backtrace:
>     [<ffffffffb60fb25c>] slab_post_alloc_hook+0x8c/0x3e0
>     [<ffffffffb6102b39>] __kmem_cache_alloc_node+0x1d9/0x2a0
>     [<ffffffffb607684e>] kmalloc_trace+0x2e/0xc0
>     [<ffffffffb6dbc064>] vlan_vid_add+0x174/0x290
>     [<ffffffffb6dbcffc>] vlan_device_event+0x19c/0x880
>     [<ffffffffb5dde4d7>] raw_notifier_call_chain+0x47/0x70
>     [<ffffffffb6ab6940>] call_netdevice_notifiers_info+0x50/0xa0
>     [<ffffffffb6ac7574>] dev_open+0x94/0xa0
>     [<ffffffffc177115e>] bond_enslave+0x34e/0x1840 [bonding]
>     [<ffffffffb6ada6b0>] do_set_master+0x90/0xb0
>     [<ffffffffb6adc5f4>] do_setlink+0x514/0x11f0
>     [<ffffffffb6ae4507>] __rtnl_newlink+0x4e7/0xa10
>     [<ffffffffb6ae4a8c>] rtnl_newlink+0x4c/0x70
>     [<ffffffffb6adf334>] rtnetlink_rcv_msg+0x184/0x5d0
>     [<ffffffffb6b6ad1e>] netlink_rcv_skb+0x5e/0x110
>     [<ffffffffb6ada0e9>] rtnetlink_rcv+0x19/0x20

VLAN ID 0 is automatically added by the 8021q driver when a net device
is opened. In this case it's a device being enslaved to a bond. I
believe the issue was exposed by the new bond test that was added in
commit 222c94ec0ad4 ("selftests: bonding: add tests for ether type
changes") as part of v6.3-rc3.

The VLAN is supposed to be removed by the 8021q driver when a net device
is closed and the bond driver indeed calls dev_close() when a slave is
removed. However, this function is a NOP when 'IFF_UP' is not set.
Unfortunately, when a bond changes its type to Ethernet this flag is
incorrectly cleared in bond_ether_setup(), causing this VLAN to linger.
As far as I can tell, it's not a new issue.

Temporary fix is [1]. Please test it although we might end up with a
different fix (needs more thinking and it's already late here).

Reproduced using [2]. You can see in the before/after output how the
flag is cleared/retained [3].

[1]
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 236e5219c811..50dc068dc259 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1777,14 +1777,15 @@ void bond_lower_state_changed(struct slave *slave)
 
 /* The bonding driver uses ether_setup() to convert a master bond device
  * to ARPHRD_ETHER, that resets the target netdevice's flags so we always
- * have to restore the IFF_MASTER flag, and only restore IFF_SLAVE if it was set
+ * have to restore the IFF_MASTER flag, and only restore IFF_SLAVE and IFF_UP
+ * if they were set
  */
 static void bond_ether_setup(struct net_device *bond_dev)
 {
-	unsigned int slave_flag = bond_dev->flags & IFF_SLAVE;
+	unsigned int flags = bond_dev->flags & (IFF_SLAVE | IFF_UP);
 
 	ether_setup(bond_dev);
-	bond_dev->flags |= IFF_MASTER | slave_flag;
+	bond_dev->flags |= IFF_MASTER | flags;
 	bond_dev->priv_flags &= ~IFF_TX_SKB_SHARING;
 }
 
[2]
#!/bin/bash

ip link add name t-nlmon type nlmon
ip link add name t-dummy type dummy
ip link add name t-bond type bond mode active-backup

ip link set dev t-bond up
ip link set dev t-nlmon master t-bond
ip link set dev t-nlmon nomaster
ip link show dev t-bond
ip link set dev t-dummy master t-bond
ip link show dev t-bond

ip link del dev t-bond
ip link del dev t-dummy
ip link del dev t-nlmon

[3]
Before:

12: t-bond: <NO-CARRIER,BROADCAST,MULTICAST,MASTER,UP> mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default qlen 1000
    link/netlink
12: t-bond: <BROADCAST,MULTICAST,MASTER,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether ce:b2:31:0a:53:83 brd ff:ff:ff:ff:ff:ff

After:

12: t-bond: <NO-CARRIER,BROADCAST,MULTICAST,MASTER,UP> mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default qlen 1000
    link/netlink
12: t-bond: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether 5a:18:e7:85:11:73 brd ff:ff:ff:ff:ff:ff