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Date: Tue, 5 Jul 2022 16:55:25 +0300
From: Ido Schimmel <idosch@...dia.com>
To: Vlad Buslov <vladbu@...dia.com>
Cc: netdev@...r.kernel.org, Maor Dickman <maord@...dia.com>,
Roopa Prabhu <roopa@...dia.com>, razor@...ckwall.org
Subject: Re: Bridge VLAN memory leak
On Mon, Jul 04, 2022 at 06:47:29PM +0300, Vlad Buslov wrote:
> Hi Ido,
>
> While implementing QinQ offload support in mlx5 I encountered a memory
> leak[0] in the bridge implementation which seems to be related to the new
> BR_VLFLAG_ADDED_BY_SWITCHDEV flag that you have recently added.
FTR, added here:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=279737939a8194f02fa352ab4476a1b241f44ef4
>
> To reproduce the issue netdevice must support bridge VLAN offload, so I
> can't provide a simple script that uses veth or anything like that.
> Instead, I'll describe the issue step-by-step:
>
> 1. Create a bridge, add offload-capable netdevs to it and assign some
> VLAN to them. __vlan_vid_add() function will set the
> BR_VLFLAG_ADDED_BY_SWITCHDEV flag since br_switchdev_port_vlan_add()
> should return 0 if dev can offload VLANs and will also skip call to
> vlan_vid_add() in such case:
>
> /* Try switchdev op first. In case it is not supported, fallback to
> * 8021q add.
> */
> err = br_switchdev_port_vlan_add(dev, v->vid, flags, false, extack);
> if (err == -EOPNOTSUPP)
> return vlan_vid_add(dev, br->vlan_proto, v->vid);
> v->priv_flags |= BR_VLFLAG_ADDED_BY_SWITCHDEV;
>
> 2. Enable filtering and set VLAN protocol to 802.1ad. That will trigger
> the following code in __br_vlan_set_proto() that re-creates existing
> VLANs with vlan_vid_add() function call whether they have the
> BR_VLFLAG_ADDED_BY_SWITCHDEV flag set or not:
>
> /* Add VLANs for the new proto to the device filter. */
> list_for_each_entry(p, &br->port_list, list) {
> vg = nbp_vlan_group(p);
> list_for_each_entry(vlan, &vg->vlan_list, vlist) {
> err = vlan_vid_add(p->dev, proto, vlan->vid);
> if (err)
> goto err_filt;
> }
> }
>
> 3. Now delete the bridge. That will delete all existing VLANs via
> __vlan_vid_del() function, which skips calling vlan_vid_del() (that is
> necessary to clean up after vlan_vid_add()) if VLAN has
> BR_VLFLAG_ADDED_BY_SWITCHDEV flag set:
>
> /* Try switchdev op first. In case it is not supported, fallback to
> * 8021q del.
> */
> err = br_switchdev_port_vlan_del(dev, v->vid);
> if (!(v->priv_flags & BR_VLFLAG_ADDED_BY_SWITCHDEV))
> vlan_vid_del(dev, br->vlan_proto, v->vid);
Looking at the code before the change, I'm pretty sure you will be able
to reproduce the leak prior to above mentioned commit:
```
- err = br_switchdev_port_vlan_del(dev, vid);
- if (err == -EOPNOTSUPP) {
- vlan_vid_del(dev, br->vlan_proto, vid);
- return 0;
- }
- return err;
```
>
>
> The issue doesn't reproduce for me anymore if I just clear the
> BR_VLFLAG_ADDED_BY_SWITCHDEV flag when re-creating VLANs on step 2.
> However, I'm not sure whether it is the right approach in this case.
> WDYT?
As a switchdev driver you already know about the new VLAN protocol via
'SWITCHDEV_ATTR_ID_BRIDGE_VLAN_PROTOCOL' so do we really need the VLANs
to be programmed again? The VLAN protocol is not communicated in
'SWITCHDEV_OBJ_ID_PORT_VLAN' anyway.
Can you try the below (compile tested only)?
```
diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 6e53dc991409..9ffd40b8270c 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c
@@ -959,6 +959,8 @@ int __br_vlan_set_proto(struct net_bridge *br, __be16 proto,
list_for_each_entry(p, &br->port_list, list) {
vg = nbp_vlan_group(p);
list_for_each_entry(vlan, &vg->vlan_list, vlist) {
+ if (vlan->priv_flags & BR_VLFLAG_ADDED_BY_SWITCHDEV)
+ continue;
err = vlan_vid_add(p->dev, proto, vlan->vid);
if (err)
goto err_filt;
@@ -973,8 +975,11 @@ int __br_vlan_set_proto(struct net_bridge *br, __be16 proto,
/* Delete VLANs for the old proto from the device filter. */
list_for_each_entry(p, &br->port_list, list) {
vg = nbp_vlan_group(p);
- list_for_each_entry(vlan, &vg->vlan_list, vlist)
+ list_for_each_entry(vlan, &vg->vlan_list, vlist) {
+ if (vlan->priv_flags & BR_VLFLAG_ADDED_BY_SWITCHDEV)
+ continue;
vlan_vid_del(p->dev, oldproto, vlan->vid);
+ }
}
return 0;
@@ -983,13 +988,19 @@ int __br_vlan_set_proto(struct net_bridge *br, __be16 proto,
attr.u.vlan_protocol = ntohs(oldproto);
switchdev_port_attr_set(br->dev, &attr, NULL);
- list_for_each_entry_continue_reverse(vlan, &vg->vlan_list, vlist)
+ list_for_each_entry_continue_reverse(vlan, &vg->vlan_list, vlist) {
+ if (vlan->priv_flags & BR_VLFLAG_ADDED_BY_SWITCHDEV)
+ continue;
vlan_vid_del(p->dev, proto, vlan->vid);
+ }
list_for_each_entry_continue_reverse(p, &br->port_list, list) {
vg = nbp_vlan_group(p);
- list_for_each_entry(vlan, &vg->vlan_list, vlist)
+ list_for_each_entry(vlan, &vg->vlan_list, vlist) {
+ if (vlan->priv_flags & BR_VLFLAG_ADDED_BY_SWITCHDEV)
+ continue;
vlan_vid_del(p->dev, proto, vlan->vid);
+ }
}
return err;
```
>
> [0]:
>
> unreferenced object 0xffff8881f6771200 (size 256):
> comm "ip", pid 446855, jiffies 4298238841 (age 55.240s)
> hex dump (first 32 bytes):
> 00 00 7f 0e 83 88 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:
> [<00000000012819ac>] vlan_vid_add+0x437/0x750
> [<00000000f2281fad>] __br_vlan_set_proto+0x289/0x920
> [<000000000632b56f>] br_changelink+0x3d6/0x13f0
> [<0000000089d25f04>] __rtnl_newlink+0x8ae/0x14c0
> [<00000000f6276baf>] rtnl_newlink+0x5f/0x90
> [<00000000746dc902>] rtnetlink_rcv_msg+0x336/0xa00
> [<000000001c2241c0>] netlink_rcv_skb+0x11d/0x340
> [<0000000010588814>] netlink_unicast+0x438/0x710
> [<00000000e1a4cd5c>] netlink_sendmsg+0x788/0xc40
> [<00000000e8992d4e>] sock_sendmsg+0xb0/0xe0
> [<00000000621b8f91>] ____sys_sendmsg+0x4ff/0x6d0
> [<000000000ea26996>] ___sys_sendmsg+0x12e/0x1b0
> [<00000000684f7e25>] __sys_sendmsg+0xab/0x130
> [<000000004538b104>] do_syscall_64+0x3d/0x90
> [<0000000091ed9678>] entry_SYSCALL_64_after_hwframe+0x46/0xb0
>
>
> Regards,
> Vlad
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