[v2] net: ipmr: fix suspicious RCU warning

Message ID 20191120152255.18928-1-anders.roxell@linaro.org
State New
Headers show
Series
  • [v2] net: ipmr: fix suspicious RCU warning
Related show

Commit Message

Anders Roxell Nov. 20, 2019, 3:22 p.m.
When booting an arm64 allmodconfig kernel on linux-next next-20191115
The following "suspicious RCU usage" warning shows up.  This bug seems
to have been introduced by commit f0ad0860d01e ("ipv4: ipmr: support
multiple tables") in 2010, but the warning was added only in this past
year by commit 28875945ba98 ("rcu: Add support for consolidated-RCU
reader checking").

[   32.496021][    T1] =============================
[   32.497616][    T1] WARNING: suspicious RCU usage
[   32.499614][    T1] 5.4.0-rc6-next-20191108-00003-gf74bac957b5c-dirty #2 Not tainted
[   32.502018][    T1] -----------------------------
[   32.503976][    T1] net/ipv4/ipmr.c:136 RCU-list traversed in non-reader section!!
[   32.506746][    T1]
[   32.506746][    T1] other info that might help us debug this:
[   32.506746][    T1]
[   32.509794][    T1]
[   32.509794][    T1] rcu_scheduler_active = 2, debug_locks = 1
[   32.512661][    T1] 1 lock held by swapper/0/1:
[   32.514169][    T1]  #0: ffffa000150dd678 (pernet_ops_rwsem){+.+.}, at: register_pernet_subsys+0x24/0x50
[   32.517621][    T1]
[   32.517621][    T1] stack backtrace:
[   32.519930][    T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-rc6-next-20191108-00003-gf74bac957b5c-dirty #2
[   32.523063][    T1] Hardware name: linux,dummy-virt (DT)
[   32.524787][    T1] Call trace:
[   32.525946][    T1]  dump_backtrace+0x0/0x2d0
[   32.527433][    T1]  show_stack+0x20/0x30
[   32.528811][    T1]  dump_stack+0x204/0x2ac
[   32.530258][    T1]  lockdep_rcu_suspicious+0xf4/0x108
[   32.531993][    T1]  ipmr_get_table+0xc8/0x170
[   32.533496][    T1]  ipmr_new_table+0x48/0xa0
[   32.535002][    T1]  ipmr_net_init+0xe8/0x258
[   32.536465][    T1]  ops_init+0x280/0x2d8
[   32.537876][    T1]  register_pernet_operations+0x210/0x420
[   32.539707][    T1]  register_pernet_subsys+0x30/0x50
[   32.541372][    T1]  ip_mr_init+0x54/0x180
[   32.542785][    T1]  inet_init+0x25c/0x3e8
[   32.544186][    T1]  do_one_initcall+0x4c0/0xad8
[   32.545757][    T1]  kernel_init_freeable+0x3e0/0x500
[   32.547443][    T1]  kernel_init+0x14/0x1f0
[   32.548875][    T1]  ret_from_fork+0x10/0x18

This commit therefore holds RTNL mutex around the problematic code path,
which is function ipmr_rules_init() in ipmr_net_init().  This commit
also adds a lockdep_rtnl_is_held() check to the ipmr_for_each_table()
macro.

Suggested-by: David Miller <davem@davemloft.net>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>

Signed-off-by: Anders Roxell <anders.roxell@linaro.org>

---
 net/ipv4/ipmr.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

-- 
2.20.1

Comments

Eric Dumazet Nov. 20, 2019, 5:45 p.m. | #1
On 11/20/19 7:22 AM, Anders Roxell wrote:
> When booting an arm64 allmodconfig kernel on linux-next next-20191115

> The following "suspicious RCU usage" warning shows up.  This bug seems

> to have been introduced by commit f0ad0860d01e ("ipv4: ipmr: support

> multiple tables") in 2010, but the warning was added only in this past

> year by commit 28875945ba98 ("rcu: Add support for consolidated-RCU

> reader checking").

> 

> [   32.496021][    T1] =============================

> [   32.497616][    T1] WARNING: suspicious RCU usage

> [   32.499614][    T1] 5.4.0-rc6-next-20191108-00003-gf74bac957b5c-dirty #2 Not tainted

> [   32.502018][    T1] -----------------------------

> [   32.503976][    T1] net/ipv4/ipmr.c:136 RCU-list traversed in non-reader section!!

> [   32.506746][    T1]

> [   32.506746][    T1] other info that might help us debug this:

> [   32.506746][    T1]

> [   32.509794][    T1]

> [   32.509794][    T1] rcu_scheduler_active = 2, debug_locks = 1

> [   32.512661][    T1] 1 lock held by swapper/0/1:

> [   32.514169][    T1]  #0: ffffa000150dd678 (pernet_ops_rwsem){+.+.}, at: register_pernet_subsys+0x24/0x50

> [   32.517621][    T1]

> [   32.517621][    T1] stack backtrace:

> [   32.519930][    T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-rc6-next-20191108-00003-gf74bac957b5c-dirty #2

> [   32.523063][    T1] Hardware name: linux,dummy-virt (DT)

> [   32.524787][    T1] Call trace:

> [   32.525946][    T1]  dump_backtrace+0x0/0x2d0

> [   32.527433][    T1]  show_stack+0x20/0x30

> [   32.528811][    T1]  dump_stack+0x204/0x2ac

> [   32.530258][    T1]  lockdep_rcu_suspicious+0xf4/0x108

> [   32.531993][    T1]  ipmr_get_table+0xc8/0x170

> [   32.533496][    T1]  ipmr_new_table+0x48/0xa0

> [   32.535002][    T1]  ipmr_net_init+0xe8/0x258

> [   32.536465][    T1]  ops_init+0x280/0x2d8

> [   32.537876][    T1]  register_pernet_operations+0x210/0x420

> [   32.539707][    T1]  register_pernet_subsys+0x30/0x50

> [   32.541372][    T1]  ip_mr_init+0x54/0x180

> [   32.542785][    T1]  inet_init+0x25c/0x3e8

> [   32.544186][    T1]  do_one_initcall+0x4c0/0xad8

> [   32.545757][    T1]  kernel_init_freeable+0x3e0/0x500

> [   32.547443][    T1]  kernel_init+0x14/0x1f0

> [   32.548875][    T1]  ret_from_fork+0x10/0x18

> 

> This commit therefore holds RTNL mutex around the problematic code path,

> which is function ipmr_rules_init() in ipmr_net_init().  This commit

> also adds a lockdep_rtnl_is_held() check to the ipmr_for_each_table()

> macro.

> 

> Suggested-by: David Miller <davem@davemloft.net>

> Reviewed-by: Paul E. McKenney <paulmck@kernel.org>

> Signed-off-by: Anders Roxell <anders.roxell@linaro.org>

> ---

>  net/ipv4/ipmr.c | 5 ++++-

>  1 file changed, 4 insertions(+), 1 deletion(-)

> 

> diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c

> index 6e68def66822..53dff9a0e60a 100644

> --- a/net/ipv4/ipmr.c

> +++ b/net/ipv4/ipmr.c

> @@ -110,7 +110,8 @@ static void ipmr_expire_process(struct timer_list *t);

>  

>  #ifdef CONFIG_IP_MROUTE_MULTIPLE_TABLES

>  #define ipmr_for_each_table(mrt, net) \

> -	list_for_each_entry_rcu(mrt, &net->ipv4.mr_tables, list)

> +	list_for_each_entry_rcu(mrt, &net->ipv4.mr_tables, list, \

> +				lockdep_rtnl_is_held())

>  

>  static struct mr_table *ipmr_mr_table_iter(struct net *net,

>  					   struct mr_table *mrt)

> @@ -3086,7 +3087,9 @@ static int __net_init ipmr_net_init(struct net *net)

>  	if (err)

>  		goto ipmr_notifier_fail;

>  

> +	rtnl_lock();

>  	err = ipmr_rules_init(net);

> +	rtnl_unlock();

>  	if (err < 0)

>  		goto ipmr_rules_fail;


Hmmm... this might have performance impact for creation of a new netns

Since the 'struct net' is not yet fully initialized (thus published/visible),
should we really have to grab RTNL (again) only to silence a warning ?

What about the following alternative ?

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 6e68def66822f47fc08d94eddd32a4bd4f9fdfb0..b6dcdce08f1d82c83756a319623e24ae0174092c 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -94,7 +94,7 @@ static DEFINE_SPINLOCK(mfc_unres_lock);
 
 static struct kmem_cache *mrt_cachep __ro_after_init;
 
-static struct mr_table *ipmr_new_table(struct net *net, u32 id);
+static struct mr_table *ipmr_new_table(struct net *net, u32 id, bool init);
 static void ipmr_free_table(struct mr_table *mrt);
 
 static void ip_mr_forward(struct net *net, struct mr_table *mrt,
@@ -245,7 +245,7 @@ static int __net_init ipmr_rules_init(struct net *net)
 
        INIT_LIST_HEAD(&net->ipv4.mr_tables);
 
-       mrt = ipmr_new_table(net, RT_TABLE_DEFAULT);
+       mrt = ipmr_new_table(net, RT_TABLE_DEFAULT, true);
        if (IS_ERR(mrt)) {
                err = PTR_ERR(mrt);
                goto err1;
@@ -322,7 +322,7 @@ static int __net_init ipmr_rules_init(struct net *net)
 {
        struct mr_table *mrt;
 
-       mrt = ipmr_new_table(net, RT_TABLE_DEFAULT);
+       mrt = ipmr_new_table(net, RT_TABLE_DEFAULT, true);
        if (IS_ERR(mrt))
                return PTR_ERR(mrt);
        net->ipv4.mrt = mrt;
@@ -392,7 +392,7 @@ static struct mr_table_ops ipmr_mr_table_ops = {
        .cmparg_any = &ipmr_mr_table_ops_cmparg_any,
 };
 
-static struct mr_table *ipmr_new_table(struct net *net, u32 id)
+static struct mr_table *ipmr_new_table(struct net *net, u32 id, bool init)
 {
        struct mr_table *mrt;
 
@@ -400,9 +400,11 @@ static struct mr_table *ipmr_new_table(struct net *net, u32 id)
        if (id != RT_TABLE_DEFAULT && id >= 1000000000)
                return ERR_PTR(-EINVAL);
 
-       mrt = ipmr_get_table(net, id);
-       if (mrt)
-               return mrt;
+       if (!init) {
+               mrt = ipmr_get_table(net, id);
+               if (mrt)
+                       return mrt;
+       }
 
        return mr_table_alloc(net, id, &ipmr_mr_table_ops,
                              ipmr_expire_process, ipmr_new_table_set);
@@ -1547,7 +1549,7 @@ int ip_mroute_setsockopt(struct sock *sk, int optname, char __user *optval,
                if (sk == rtnl_dereference(mrt->mroute_sk)) {
                        ret = -EBUSY;
                } else {
-                       mrt = ipmr_new_table(net, uval);
+                       mrt = ipmr_new_table(net, uval, false);
                        if (IS_ERR(mrt))
                                ret = PTR_ERR(mrt);
                        else
Anders Roxell Nov. 21, 2019, 10:17 a.m. | #2
On Thu, 21 Nov 2019 at 08:15, Anders Roxell <anders.roxell@linaro.org> wrote:
>

> On Wed, 20 Nov 2019 at 18:45, Eric Dumazet <eric.dumazet@gmail.com> wrote:

> >

> >

> >

> > On 11/20/19 7:22 AM, Anders Roxell wrote:


[snippet]

> > > +     rtnl_lock();

> > >       err = ipmr_rules_init(net);

> > > +     rtnl_unlock();

> > >       if (err < 0)

> > >               goto ipmr_rules_fail;

> >

> > Hmmm... this might have performance impact for creation of a new netns

> >

> > Since the 'struct net' is not yet fully initialized (thus published/visible),

> > should we really have to grab RTNL (again) only to silence a warning ?

> >

> > What about the following alternative ?

>

> I tried what you suggested, unfortunately, I still got the warning.


I was wrong, so if I also add "lockdep_rtnl_is_held()" to the
"ipmr_for_each_table()" macro it works.

>

>

> [   43.253850][    T1] =============================

> [   43.255473][    T1] WARNING: suspicious RCU usage

> [   43.259068][    T1]

> 5.4.0-rc8-next-20191120-00003-g3aa7c2a8649e-dirty #6 Not tainted

> [   43.263078][    T1] -----------------------------

> [   43.265134][    T1] net/ipv4/ipmr.c:1759 RCU-list traversed in

> non-reader section!!

> [   43.267587][    T1]

> [   43.267587][    T1] other info that might help us debug this:

> [   43.267587][    T1]

> [   43.271129][    T1]

> [   43.271129][    T1] rcu_scheduler_active = 2, debug_locks = 1

> [   43.274021][    T1] 2 locks held by swapper/0/1:

> [   43.275532][    T1]  #0: ffff000065abeaa0 (&dev->mutex){....}, at:

> __device_driver_lock+0xa0/0xb0

> [   43.278930][    T1]  #1: ffffa000153017f0 (rtnl_mutex){+.+.}, at:

> rtnl_lock+0x1c/0x28

> [   43.282023][    T1]

> [   43.282023][    T1] stack backtrace:

> [   43.283921][    T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted

> 5.4.0-rc8-next-20191120-00003-g3aa7c2a8649e-dirty #6

> [   43.287152][    T1] Hardware name: linux,dummy-virt (DT)

> [   43.288920][    T1] Call trace:

> [   43.290057][    T1]  dump_backtrace+0x0/0x2d0

> [   43.291535][    T1]  show_stack+0x20/0x30

> [   43.292967][    T1]  dump_stack+0x204/0x2ac

> [   43.294423][    T1]  lockdep_rcu_suspicious+0xf4/0x108

> [   43.296163][    T1]  ipmr_device_event+0x100/0x1e8

> [   43.297812][    T1]  notifier_call_chain+0x100/0x1a8

> [   43.299486][    T1]  raw_notifier_call_chain+0x38/0x48

> [   43.301248][    T1]  call_netdevice_notifiers_info+0x128/0x148

> [   43.303158][    T1]  rollback_registered_many+0x684/0xb48

> [   43.304963][    T1]  rollback_registered+0xd8/0x150

> [   43.306595][    T1]  unregister_netdevice_queue+0x194/0x1b8

> [   43.308406][    T1]  unregister_netdev+0x24/0x38

> [   43.310012][    T1]  virtnet_remove+0x44/0x78

> [   43.311519][    T1]  virtio_dev_remove+0x5c/0xc0

> [   43.313114][    T1]  really_probe+0x508/0x920

> [   43.314635][    T1]  driver_probe_device+0x164/0x230

> [   43.316337][    T1]  device_driver_attach+0x8c/0xc0

> [   43.318024][    T1]  __driver_attach+0x1e0/0x1f8

> [   43.319584][    T1]  bus_for_each_dev+0xf0/0x188

> [   43.321169][    T1]  driver_attach+0x34/0x40

> [   43.322645][    T1]  bus_add_driver+0x204/0x3c8

> [   43.324202][    T1]  driver_register+0x160/0x1f8

> [   43.325788][    T1]  register_virtio_driver+0x7c/0x88

> [   43.327480][    T1]  virtio_net_driver_init+0xa8/0xf4

> [   43.329196][    T1]  do_one_initcall+0x4c0/0xad8

> [   43.330767][    T1]  kernel_init_freeable+0x3e0/0x500

> [   43.332444][    T1]  kernel_init+0x14/0x1f0

> [   43.333901][    T1]  ret_from_fork+0x10/0x18

>

>

> Cheers,

> Anders

>

> >

> > diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c

> > index 6e68def66822f47fc08d94eddd32a4bd4f9fdfb0..b6dcdce08f1d82c83756a319623e24ae0174092c 100644

> > --- a/net/ipv4/ipmr.c

> > +++ b/net/ipv4/ipmr.c

> > @@ -94,7 +94,7 @@ static DEFINE_SPINLOCK(mfc_unres_lock);

> >

> >  static struct kmem_cache *mrt_cachep __ro_after_init;

> >

> > -static struct mr_table *ipmr_new_table(struct net *net, u32 id);

> > +static struct mr_table *ipmr_new_table(struct net *net, u32 id, bool init);

> >  static void ipmr_free_table(struct mr_table *mrt);

> >


 static void ip_mr_forward(struct net *net, struct mr_table *mrt,
@@ -110,7 +110,8 @@ static void ipmr_expire_process(struct timer_list *t);

 #ifdef CONFIG_IP_MROUTE_MULTIPLE_TABLES
 #define ipmr_for_each_table(mrt, net) \
-       list_for_each_entry_rcu(mrt, &net->ipv4.mr_tables, list)
+       list_for_each_entry_rcu(mrt, &net->ipv4.mr_tables, list, \
+                               lockdep_rtnl_is_held())
 static struct mr_table *ipmr_mr_table_iter(struct net *net,
                                           struct mr_table *mrt)


Cheers,
Anders

> >  static void ip_mr_forward(struct net *net, struct mr_table *mrt,

> > @@ -245,7 +245,7 @@ static int __net_init ipmr_rules_init(struct net *net)

> >

> >         INIT_LIST_HEAD(&net->ipv4.mr_tables);

> >

> > -       mrt = ipmr_new_table(net, RT_TABLE_DEFAULT);

> > +       mrt = ipmr_new_table(net, RT_TABLE_DEFAULT, true);

> >         if (IS_ERR(mrt)) {

> >                 err = PTR_ERR(mrt);

> >                 goto err1;

> > @@ -322,7 +322,7 @@ static int __net_init ipmr_rules_init(struct net *net)

> >  {

> >         struct mr_table *mrt;

> >

> > -       mrt = ipmr_new_table(net, RT_TABLE_DEFAULT);

> > +       mrt = ipmr_new_table(net, RT_TABLE_DEFAULT, true);

> >         if (IS_ERR(mrt))

> >                 return PTR_ERR(mrt);

> >         net->ipv4.mrt = mrt;

> > @@ -392,7 +392,7 @@ static struct mr_table_ops ipmr_mr_table_ops = {

> >         .cmparg_any = &ipmr_mr_table_ops_cmparg_any,

> >  };

> >

> > -static struct mr_table *ipmr_new_table(struct net *net, u32 id)

> > +static struct mr_table *ipmr_new_table(struct net *net, u32 id, bool init)

> >  {

> >         struct mr_table *mrt;

> >

> > @@ -400,9 +400,11 @@ static struct mr_table *ipmr_new_table(struct net *net, u32 id)

> >         if (id != RT_TABLE_DEFAULT && id >= 1000000000)

> >                 return ERR_PTR(-EINVAL);

> >

> > -       mrt = ipmr_get_table(net, id);

> > -       if (mrt)

> > -               return mrt;

> > +       if (!init) {

> > +               mrt = ipmr_get_table(net, id);

> > +               if (mrt)

> > +                       return mrt;

> > +       }

> >

> >         return mr_table_alloc(net, id, &ipmr_mr_table_ops,

> >                               ipmr_expire_process, ipmr_new_table_set);

> > @@ -1547,7 +1549,7 @@ int ip_mroute_setsockopt(struct sock *sk, int optname, char __user *optval,

> >                 if (sk == rtnl_dereference(mrt->mroute_sk)) {

> >                         ret = -EBUSY;

> >                 } else {

> > -                       mrt = ipmr_new_table(net, uval);

> > +                       mrt = ipmr_new_table(net, uval, false);

> >                         if (IS_ERR(mrt))

> >                                 ret = PTR_ERR(mrt);

> >                         else

> >

> >
Eric Dumazet Nov. 21, 2019, 5:41 p.m. | #3
On 11/21/19 2:17 AM, Anders Roxell wrote:
> On Thu, 21 Nov 2019 at 08:15, Anders Roxell <anders.roxell@linaro.org> wrote:

>>

>> On Wed, 20 Nov 2019 at 18:45, Eric Dumazet <eric.dumazet@gmail.com> wrote:

>>>

>>>

>>>

>>> On 11/20/19 7:22 AM, Anders Roxell wrote:

> 

> [snippet]

> 

>>>> +     rtnl_lock();

>>>>       err = ipmr_rules_init(net);

>>>> +     rtnl_unlock();

>>>>       if (err < 0)

>>>>               goto ipmr_rules_fail;

>>>

>>> Hmmm... this might have performance impact for creation of a new netns

>>>

>>> Since the 'struct net' is not yet fully initialized (thus published/visible),

>>> should we really have to grab RTNL (again) only to silence a warning ?

>>>

>>> What about the following alternative ?

>>

>> I tried what you suggested, unfortunately, I still got the warning.

> 

> I was wrong, so if I also add "lockdep_rtnl_is_held()" to the

> "ipmr_for_each_table()" macro it works.

> 

>>

>>

>> [   43.253850][    T1] =============================

>> [   43.255473][    T1] WARNING: suspicious RCU usage

>> [   43.259068][    T1]

>> 5.4.0-rc8-next-20191120-00003-g3aa7c2a8649e-dirty #6 Not tainted

>> [   43.263078][    T1] -----------------------------

>> [   43.265134][    T1] net/ipv4/ipmr.c:1759 RCU-list traversed in

>> non-reader section!!

>> [   43.267587][    T1]

>> [   43.267587][    T1] other info that might help us debug this:

>> [   43.267587][    T1]

>> [   43.271129][    T1]

>> [   43.271129][    T1] rcu_scheduler_active = 2, debug_locks = 1

>> [   43.274021][    T1] 2 locks held by swapper/0/1:

>> [   43.275532][    T1]  #0: ffff000065abeaa0 (&dev->mutex){....}, at:

>> __device_driver_lock+0xa0/0xb0

>> [   43.278930][    T1]  #1: ffffa000153017f0 (rtnl_mutex){+.+.}, at:

>> rtnl_lock+0x1c/0x28

>> [   43.282023][    T1]

>> [   43.282023][    T1] stack backtrace:

>> [   43.283921][    T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted

>> 5.4.0-rc8-next-20191120-00003-g3aa7c2a8649e-dirty #6

>> [   43.287152][    T1] Hardware name: linux,dummy-virt (DT)

>> [   43.288920][    T1] Call trace:

>> [   43.290057][    T1]  dump_backtrace+0x0/0x2d0

>> [   43.291535][    T1]  show_stack+0x20/0x30

>> [   43.292967][    T1]  dump_stack+0x204/0x2ac

>> [   43.294423][    T1]  lockdep_rcu_suspicious+0xf4/0x108

>> [   43.296163][    T1]  ipmr_device_event+0x100/0x1e8

>> [   43.297812][    T1]  notifier_call_chain+0x100/0x1a8

>> [   43.299486][    T1]  raw_notifier_call_chain+0x38/0x48

>> [   43.301248][    T1]  call_netdevice_notifiers_info+0x128/0x148

>> [   43.303158][    T1]  rollback_registered_many+0x684/0xb48

>> [   43.304963][    T1]  rollback_registered+0xd8/0x150

>> [   43.306595][    T1]  unregister_netdevice_queue+0x194/0x1b8

>> [   43.308406][    T1]  unregister_netdev+0x24/0x38

>> [   43.310012][    T1]  virtnet_remove+0x44/0x78

>> [   43.311519][    T1]  virtio_dev_remove+0x5c/0xc0

>> [   43.313114][    T1]  really_probe+0x508/0x920

>> [   43.314635][    T1]  driver_probe_device+0x164/0x230

>> [   43.316337][    T1]  device_driver_attach+0x8c/0xc0

>> [   43.318024][    T1]  __driver_attach+0x1e0/0x1f8

>> [   43.319584][    T1]  bus_for_each_dev+0xf0/0x188

>> [   43.321169][    T1]  driver_attach+0x34/0x40

>> [   43.322645][    T1]  bus_add_driver+0x204/0x3c8

>> [   43.324202][    T1]  driver_register+0x160/0x1f8

>> [   43.325788][    T1]  register_virtio_driver+0x7c/0x88

>> [   43.327480][    T1]  virtio_net_driver_init+0xa8/0xf4

>> [   43.329196][    T1]  do_one_initcall+0x4c0/0xad8

>> [   43.330767][    T1]  kernel_init_freeable+0x3e0/0x500

>> [   43.332444][    T1]  kernel_init+0x14/0x1f0

>> [   43.333901][    T1]  ret_from_fork+0x10/0x18

>>

>>

>> Cheers,

>> Anders

>>

>>>

>>> diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c

>>> index 6e68def66822f47fc08d94eddd32a4bd4f9fdfb0..b6dcdce08f1d82c83756a319623e24ae0174092c 100644

>>> --- a/net/ipv4/ipmr.c

>>> +++ b/net/ipv4/ipmr.c

>>> @@ -94,7 +94,7 @@ static DEFINE_SPINLOCK(mfc_unres_lock);

>>>

>>>  static struct kmem_cache *mrt_cachep __ro_after_init;

>>>

>>> -static struct mr_table *ipmr_new_table(struct net *net, u32 id);

>>> +static struct mr_table *ipmr_new_table(struct net *net, u32 id, bool init);

>>>  static void ipmr_free_table(struct mr_table *mrt);

>>>

> 

>  static void ip_mr_forward(struct net *net, struct mr_table *mrt,

> @@ -110,7 +110,8 @@ static void ipmr_expire_process(struct timer_list *t);

> 

>  #ifdef CONFIG_IP_MROUTE_MULTIPLE_TABLES

>  #define ipmr_for_each_table(mrt, net) \

> -       list_for_each_entry_rcu(mrt, &net->ipv4.mr_tables, list)

> +       list_for_each_entry_rcu(mrt, &net->ipv4.mr_tables, list, \

> +                               lockdep_rtnl_is_held())

>  static struct mr_table *ipmr_mr_table_iter(struct net *net,

>                                            struct mr_table *mrt)

> 

> 

> Cheers,

> Anders


That is great, I guess we can submit the two patches in a series.

Patch

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 6e68def66822..53dff9a0e60a 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -110,7 +110,8 @@  static void ipmr_expire_process(struct timer_list *t);
 
 #ifdef CONFIG_IP_MROUTE_MULTIPLE_TABLES
 #define ipmr_for_each_table(mrt, net) \
-	list_for_each_entry_rcu(mrt, &net->ipv4.mr_tables, list)
+	list_for_each_entry_rcu(mrt, &net->ipv4.mr_tables, list, \
+				lockdep_rtnl_is_held())
 
 static struct mr_table *ipmr_mr_table_iter(struct net *net,
 					   struct mr_table *mrt)
@@ -3086,7 +3087,9 @@  static int __net_init ipmr_net_init(struct net *net)
 	if (err)
 		goto ipmr_notifier_fail;
 
+	rtnl_lock();
 	err = ipmr_rules_init(net);
+	rtnl_unlock();
 	if (err < 0)
 		goto ipmr_rules_fail;