[PATCH net-next] ip6_vti: fix memleak on netns dismantle

[PATCH net-next] ip6_vti: fix memleak on netns dismantle

[Florian Westphal]

kmemleak reports net_device resources are no longer released, restore
needs_free_netdev toggle.  Sample backtrace:

unreferenced object 0xffff88810874f000 (size 4096): [..]
    [<00000000a2b8af8b>] __kmalloc_node+0x209/0x290
    [<0000000040b0a1a9>] alloc_netdev_mqs+0x58/0x470
    [<00000000b4be1e78>] vti6_init_net+0x94/0x230
    [<000000008830c1ea>] ops_init+0x32/0xc0
    [<000000006a26fa8f>] setup_net+0x134/0x2e0
[..]

Cc: Breno Leitao <leitao@debian.org>
Fixes: a9b2d55a8f1e ("ip6_vti: Do not use custom stat allocator")
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/ipv6/ip6_vti.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
index 4d68a0777b0c..78344cf3867e 100644
--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -901,6 +901,7 @@ static void vti6_dev_setup(struct net_device *dev)
 {
 	dev->netdev_ops = &vti6_netdev_ops;
 	dev->header_ops = &ip_tunnel_header_ops;
+	dev->needs_free_netdev = true;
 
 	dev->pcpu_stat_type = NETDEV_PCPU_STAT_TSTATS;
 	dev->type = ARPHRD_TUNNEL6;
-- 
2.43.2

Re: [PATCH net-next] ip6_vti: fix memleak on netns dismantle

[Simon Horman]

+ Steffen Klassert, Herbert Xu, David Ahern

On Mon, Apr 15, 2024 at 02:23:44PM +0200, Florian Westphal wrote:
> kmemleak reports net_device resources are no longer released, restore
> needs_free_netdev toggle.  Sample backtrace:
> 
> unreferenced object 0xffff88810874f000 (size 4096): [..]
>     [<00000000a2b8af8b>] __kmalloc_node+0x209/0x290
>     [<0000000040b0a1a9>] alloc_netdev_mqs+0x58/0x470
>     [<00000000b4be1e78>] vti6_init_net+0x94/0x230
>     [<000000008830c1ea>] ops_init+0x32/0xc0
>     [<000000006a26fa8f>] setup_net+0x134/0x2e0
> [..]
> 
> Cc: Breno Leitao <leitao@debian.org>
> Fixes: a9b2d55a8f1e ("ip6_vti: Do not use custom stat allocator")
> Signed-off-by: Florian Westphal <fw@strlen.de>

Reviewed-by: Simon Horman <horms@kernel.org>

> ---
>  net/ipv6/ip6_vti.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
> index 4d68a0777b0c..78344cf3867e 100644
> --- a/net/ipv6/ip6_vti.c
> +++ b/net/ipv6/ip6_vti.c
> @@ -901,6 +901,7 @@ static void vti6_dev_setup(struct net_device *dev)
>  {
>  	dev->netdev_ops = &vti6_netdev_ops;
>  	dev->header_ops = &ip_tunnel_header_ops;
> +	dev->needs_free_netdev = true;
>  
>  	dev->pcpu_stat_type = NETDEV_PCPU_STAT_TSTATS;
>  	dev->type = ARPHRD_TUNNEL6;
> -- 
> 2.43.2
> 
> 

Re: [PATCH net-next] ip6_vti: fix memleak on netns dismantle

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 15 Apr 2024 14:23:44 +0200 you wrote:
> kmemleak reports net_device resources are no longer released, restore
> needs_free_netdev toggle.  Sample backtrace:
> 
> unreferenced object 0xffff88810874f000 (size 4096): [..]
>     [<00000000a2b8af8b>] __kmalloc_node+0x209/0x290
>     [<0000000040b0a1a9>] alloc_netdev_mqs+0x58/0x470
>     [<00000000b4be1e78>] vti6_init_net+0x94/0x230
>     [<000000008830c1ea>] ops_init+0x32/0xc0
>     [<000000006a26fa8f>] setup_net+0x134/0x2e0
> [..]
> 
> [...]

Here is the summary with links:
  - [net-next] ip6_vti: fix memleak on netns dismantle
    https://git.kernel.org/netdev/net-next/c/86600ea11dc1

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH net-next] ip6_vti: fix memleak on netns dismantle

[Breno Leitao]

Hello Florian,

On Mon, Apr 15, 2024 at 02:23:44PM +0200, Florian Westphal wrote:
> kmemleak reports net_device resources are no longer released, restore
> needs_free_netdev toggle.  Sample backtrace:
> 
> unreferenced object 0xffff88810874f000 (size 4096): [..]
>     [<00000000a2b8af8b>] __kmalloc_node+0x209/0x290
>     [<0000000040b0a1a9>] alloc_netdev_mqs+0x58/0x470
>     [<00000000b4be1e78>] vti6_init_net+0x94/0x230
>     [<000000008830c1ea>] ops_init+0x32/0xc0
>     [<000000006a26fa8f>] setup_net+0x134/0x2e0
> [..]
> 
> Cc: Breno Leitao <leitao@debian.org>
> Fixes: a9b2d55a8f1e ("ip6_vti: Do not use custom stat allocator")
> Signed-off-by: Florian Westphal <fw@strlen.de>
> ---
>  net/ipv6/ip6_vti.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
> index 4d68a0777b0c..78344cf3867e 100644
> --- a/net/ipv6/ip6_vti.c
> +++ b/net/ipv6/ip6_vti.c
> @@ -901,6 +901,7 @@ static void vti6_dev_setup(struct net_device *dev)
>  {
>  	dev->netdev_ops = &vti6_netdev_ops;
>  	dev->header_ops = &ip_tunnel_header_ops;
> +	dev->needs_free_netdev = true;

Thanks for the fix!

Could you help me to understand how needs_free_netdev will trigger the
free()here?

I _though_ that any device that is being unregistered would have the stats
freed.

This is the flow I am reading:

1) When the device is unregistered, then it is marked as todo:

	unregister_netdevice_many_notify() {
		list_for_each_entry(dev, head, unreg_list) {
			net_set_todo(dev);
		}
	}

2) Then, "run_todo" will run later, and it does:
	netdev_run_todo() {
		list_for_each_entry_safe(dev, tmp, &list, todo_list) {
		if (unlikely(dev->reg_state != NETREG_UNREGISTERING)) {
			netdev_WARN(dev, "run_todo but not unregistering\n");
			list_del(&dev->todo_list);
			continue;
		}

		while (!list_empty(&list)) {
			netdev_do_free_pcpu_stats(dev);
		}

	}

Thank you!

Re: [PATCH net-next] ip6_vti: fix memleak on netns dismantle

[Eric Dumazet]

On Tue, Apr 23, 2024 at 11:46 AM Breno Leitao <leitao@debian.org> wrote:
>
> Hello Florian,
>
> On Mon, Apr 15, 2024 at 02:23:44PM +0200, Florian Westphal wrote:
> > kmemleak reports net_device resources are no longer released, restore
> > needs_free_netdev toggle.  Sample backtrace:
> >
> > unreferenced object 0xffff88810874f000 (size 4096): [..]
> >     [<00000000a2b8af8b>] __kmalloc_node+0x209/0x290
> >     [<0000000040b0a1a9>] alloc_netdev_mqs+0x58/0x470
> >     [<00000000b4be1e78>] vti6_init_net+0x94/0x230
> >     [<000000008830c1ea>] ops_init+0x32/0xc0
> >     [<000000006a26fa8f>] setup_net+0x134/0x2e0
> > [..]
> >
> > Cc: Breno Leitao <leitao@debian.org>
> > Fixes: a9b2d55a8f1e ("ip6_vti: Do not use custom stat allocator")
> > Signed-off-by: Florian Westphal <fw@strlen.de>
> > ---
> >  net/ipv6/ip6_vti.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
> > index 4d68a0777b0c..78344cf3867e 100644
> > --- a/net/ipv6/ip6_vti.c
> > +++ b/net/ipv6/ip6_vti.c
> > @@ -901,6 +901,7 @@ static void vti6_dev_setup(struct net_device *dev)
> >  {
> >       dev->netdev_ops = &vti6_netdev_ops;
> >       dev->header_ops = &ip_tunnel_header_ops;
> > +     dev->needs_free_netdev = true;
>
> Thanks for the fix!
>
> Could you help me to understand how needs_free_netdev will trigger the
> free()here?
>
> I _though_ that any device that is being unregistered would have the stats
> freed.
>
> This is the flow I am reading:
>
> 1) When the device is unregistered, then it is marked as todo:
>
>         unregister_netdevice_many_notify() {
>                 list_for_each_entry(dev, head, unreg_list) {
>                         net_set_todo(dev);
>                 }
>         }
>
> 2) Then, "run_todo" will run later, and it does:
>         netdev_run_todo() {
>                 list_for_each_entry_safe(dev, tmp, &list, todo_list) {
>                 if (unlikely(dev->reg_state != NETREG_UNREGISTERING)) {
>                         netdev_WARN(dev, "run_todo but not unregistering\n");
>                         list_del(&dev->todo_list);
>                         continue;
>                 }
>
>                 while (!list_empty(&list)) {
>                         netdev_do_free_pcpu_stats(dev);

The relevant part is missing:

                         if (dev->needs_free_netdev)
                                  free_netdev(dev);

>                 }
>
>         }
>
> Thank you!

I do not think Florian patch has anything to do with free_pcpu_stats()

Please take a look at

git show cf124db566e -- net/ipv6/ip6_vti.c

Re: [PATCH net-next] ip6_vti: fix memleak on netns dismantle

[Breno Leitao]

Hello Eric,

On Tue, Apr 23, 2024 at 09:53:45PM +0200, Eric Dumazet wrote:
> On Tue, Apr 23, 2024 at 11:46 AM Breno Leitao <leitao@debian.org> wrote:
> >
> > Hello Florian,
> >
> > On Mon, Apr 15, 2024 at 02:23:44PM +0200, Florian Westphal wrote:
> > > kmemleak reports net_device resources are no longer released, restore
> > > needs_free_netdev toggle.  Sample backtrace:
> > >
> > > unreferenced object 0xffff88810874f000 (size 4096): [..]
> > >     [<00000000a2b8af8b>] __kmalloc_node+0x209/0x290
> > >     [<0000000040b0a1a9>] alloc_netdev_mqs+0x58/0x470
> > >     [<00000000b4be1e78>] vti6_init_net+0x94/0x230
> > >     [<000000008830c1ea>] ops_init+0x32/0xc0
> > >     [<000000006a26fa8f>] setup_net+0x134/0x2e0
> > > [..]
> > >
> > > Cc: Breno Leitao <leitao@debian.org>
> > > Fixes: a9b2d55a8f1e ("ip6_vti: Do not use custom stat allocator")
> > > Signed-off-by: Florian Westphal <fw@strlen.de>
> > > ---
> > >  net/ipv6/ip6_vti.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
> > > index 4d68a0777b0c..78344cf3867e 100644
> > > --- a/net/ipv6/ip6_vti.c
> > > +++ b/net/ipv6/ip6_vti.c
> > > @@ -901,6 +901,7 @@ static void vti6_dev_setup(struct net_device *dev)
> > >  {
> > >       dev->netdev_ops = &vti6_netdev_ops;
> > >       dev->header_ops = &ip_tunnel_header_ops;
> > > +     dev->needs_free_netdev = true;
> >
> > Thanks for the fix!
> >
> > Could you help me to understand how needs_free_netdev will trigger the
> > free()here?
> >
> > I _though_ that any device that is being unregistered would have the stats
> > freed.
> >
> > This is the flow I am reading:
> >
> > 1) When the device is unregistered, then it is marked as todo:
> >
> >         unregister_netdevice_many_notify() {
> >                 list_for_each_entry(dev, head, unreg_list) {
> >                         net_set_todo(dev);
> >                 }
> >         }
> >
> > 2) Then, "run_todo" will run later, and it does:
> >         netdev_run_todo() {
> >                 list_for_each_entry_safe(dev, tmp, &list, todo_list) {
> >                 if (unlikely(dev->reg_state != NETREG_UNREGISTERING)) {
> >                         netdev_WARN(dev, "run_todo but not unregistering\n");
> >                         list_del(&dev->todo_list);
> >                         continue;
> >                 }
> >
> >                 while (!list_empty(&list)) {
> >                         netdev_do_free_pcpu_stats(dev);
> 
> The relevant part is missing:
> 
>                          if (dev->needs_free_netdev)
>                                   free_netdev(dev);
> 
> >                 }
> >
> >         }
> >
> > Thank you!
> 
> I do not think Florian patch has anything to do with free_pcpu_stats()

That makes total sense now.

I though the memory that was being leaked was related to pcpu stats,
since this is was I was supposedly changing, but, it is not.

The regression is not related to the fact that 
a9b2d55a8f1e ("ip6_vti: Do not use custom stat allocator") removed
the following line wrongly:

	-dev->needs_free_netdev = true;

Everything is clear now.
Thanks!