[net] net: ping6: Fix possible leaked pernet namespace in pingv6_init()

  When IPv6 module initializing in pingv6_init(), inet6_register_protosw()
is possible to fail but returns without any error cleanup.

This leaves wild ops in namespace list and when another module tries to
add or delete pernet namespace it triggers page fault.
Although IPv6 cannot be unloaded now, this error should still be handled
to avoid kernel panic during IPv6 initialization.

BUG: unable to handle page fault for address: fffffbfff80bab69
CPU: 0 PID: 434 Comm: modprobe
RIP: 0010:unregister_pernet_operations+0xc9/0x450
Call Trace:
 <TASK>
 unregister_pernet_subsys+0x31/0x3e
 nf_tables_module_exit+0x44/0x6a [nf_tables]
 __do_sys_delete_module.constprop.0+0x34f/0x5b0
 ...

Fix it by adding error handling in pingv6_init(), and add a helper
function pingv6_ops_unset to avoid duplicate code.

Fixes: d862e5461423 ("net: ipv6: Implement /proc/net/icmp6.")
Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com>
---
 net/ipv6/ping.c | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)
  

From:   Chen Zhongjin <chenzhongjin@huawei.com>
Date:   Thu, 3 Nov 2022 17:03:45 +0800
> When IPv6 module initializing in pingv6_init(), inet6_register_protosw()
> is possible to fail but returns without any error cleanup.

The change itself looks sane, but how does it fail ?
It seems inet6_register_protosw() never fails for pingv6_protosw.
Am I missing something ?

---8<---
static struct inet_protosw pingv6_protosw = {
	.type =      SOCK_DGRAM,         <-- .type < SOCK_MAX
	.protocol =  IPPROTO_ICMPV6,
	.prot =      &pingv6_prot,
	.ops =       &inet6_sockraw_ops,
	.flags =     INET_PROTOSW_REUSE,  <-- always makes `answer` NULL
};

int inet6_register_protosw(struct inet_protosw *p)
{
	struct list_head *lh;
	struct inet_protosw *answer;
	struct list_head *last_perm;
	int protocol = p->protocol;
	int ret;

	spin_lock_bh(&inetsw6_lock);

	ret = -EINVAL;
	if (p->type >= SOCK_MAX)
		goto out_illegal;

	/* If we are trying to override a permanent protocol, bail. */
	answer = NULL;
	ret = -EPERM;
	last_perm = &inetsw6[p->type];
	list_for_each(lh, &inetsw6[p->type]) {
		answer = list_entry(lh, struct inet_protosw, list);

		/* Check only the non-wild match. */
		if (INET_PROTOSW_PERMANENT & answer->flags) {
			if (protocol == answer->protocol)
				break;
			last_perm = lh;
		}

		answer = NULL;
	}
	if (answer)
		goto out_permanent;
...
	list_add_rcu(&p->list, last_perm);
	ret = 0;
out:
	spin_unlock_bh(&inetsw6_lock);
	return ret;

out_permanent:
	pr_err("Attempt to override permanent protocol %d\n", protocol);
	goto out;

out_illegal:
	pr_err("Ignoring attempt to register invalid socket type %d\n",
	       p->type);
	goto out;
}
---8<---

> 
> This leaves wild ops in namespace list and when another module tries to
> add or delete pernet namespace it triggers page fault.
> Although IPv6 cannot be unloaded now, this error should still be handled
> to avoid kernel panic during IPv6 initialization.
> 
> BUG: unable to handle page fault for address: fffffbfff80bab69
> CPU: 0 PID: 434 Comm: modprobe
> RIP: 0010:unregister_pernet_operations+0xc9/0x450
> Call Trace:
>  <TASK>
>  unregister_pernet_subsys+0x31/0x3e
>  nf_tables_module_exit+0x44/0x6a [nf_tables]
>  __do_sys_delete_module.constprop.0+0x34f/0x5b0
>  ...
> 
> Fix it by adding error handling in pingv6_init(), and add a helper

I'm wondering this could be another place.


> function pingv6_ops_unset to avoid duplicate code.
> 
> Fixes: d862e5461423 ("net: ipv6: Implement /proc/net/icmp6.")
> Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com>
> ---
>  net/ipv6/ping.c | 30 ++++++++++++++++++++++--------
>  1 file changed, 22 insertions(+), 8 deletions(-)
> 
> diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
> index 86c26e48d065..5df688dd5208 100644
> --- a/net/ipv6/ping.c
> +++ b/net/ipv6/ping.c
> @@ -277,10 +277,21 @@ static struct pernet_operations ping_v6_net_ops = {
>  };
>  #endif
>  
> +static void pingv6_ops_unset(void)
> +{
> +	pingv6_ops.ipv6_recv_error = dummy_ipv6_recv_error;
> +	pingv6_ops.ip6_datagram_recv_common_ctl = dummy_ip6_datagram_recv_ctl;
> +	pingv6_ops.ip6_datagram_recv_specific_ctl = dummy_ip6_datagram_recv_ctl;
> +	pingv6_ops.icmpv6_err_convert = dummy_icmpv6_err_convert;
> +	pingv6_ops.ipv6_icmp_error = dummy_ipv6_icmp_error;
> +	pingv6_ops.ipv6_chk_addr = dummy_ipv6_chk_addr;
> +}
> +
>  int __init pingv6_init(void)
>  {
> +	int ret;
>  #ifdef CONFIG_PROC_FS
> -	int ret = register_pernet_subsys(&ping_v6_net_ops);
> +	ret = register_pernet_subsys(&ping_v6_net_ops);
>  	if (ret)
>  		return ret;
>  #endif
> @@ -291,7 +302,15 @@ int __init pingv6_init(void)
>  	pingv6_ops.icmpv6_err_convert = icmpv6_err_convert;
>  	pingv6_ops.ipv6_icmp_error = ipv6_icmp_error;
>  	pingv6_ops.ipv6_chk_addr = ipv6_chk_addr;
> -	return inet6_register_protosw(&pingv6_protosw);
> +
> +	ret = inet6_register_protosw(&pingv6_protosw);
> +	if (ret) {
> +		pingv6_ops_unset();
> +#ifdef CONFIG_PROC_FS
> +		unregister_pernet_subsys(&ping_v6_net_ops);
> +#endif
> +	}
> +	return ret;
>  }
>  
>  /* This never gets called because it's not possible to unload the ipv6 module,
> @@ -299,12 +318,7 @@ int __init pingv6_init(void)
>   */
>  void pingv6_exit(void)
>  {
> -	pingv6_ops.ipv6_recv_error = dummy_ipv6_recv_error;
> -	pingv6_ops.ip6_datagram_recv_common_ctl = dummy_ip6_datagram_recv_ctl;
> -	pingv6_ops.ip6_datagram_recv_specific_ctl = dummy_ip6_datagram_recv_ctl;
> -	pingv6_ops.icmpv6_err_convert = dummy_icmpv6_err_convert;
> -	pingv6_ops.ipv6_icmp_error = dummy_ipv6_icmp_error;
> -	pingv6_ops.ipv6_chk_addr = dummy_ipv6_chk_addr;
> +	pingv6_ops_unset();
>  #ifdef CONFIG_PROC_FS
>  	unregister_pernet_subsys(&ping_v6_net_ops);
>  #endif
> -- 
> 2.17.1
  

Hi,

On 2022/11/4 0:58, Kuniyuki Iwashima wrote:
> From:   Chen Zhongjin <chenzhongjin@huawei.com>
> Date:   Thu, 3 Nov 2022 17:03:45 +0800
>> When IPv6 module initializing in pingv6_init(), inet6_register_protosw()
>> is possible to fail but returns without any error cleanup.
> The change itself looks sane, but how does it fail ?
> It seems inet6_register_protosw() never fails for pingv6_protosw.
> Am I missing something ?

Thanks for reminding! I only injected error return value for functions 
but didn't notice the inner logic.

Rechecked and find you are right that inet6_register_protosw() is safe 
for this case.

Sorry for bothering, please reject this. Will check carefully next time.


Best,

Chen

> ---8<---
> static struct inet_protosw pingv6_protosw = {
> 	.type =      SOCK_DGRAM,         <-- .type < SOCK_MAX
> 	.protocol =  IPPROTO_ICMPV6,
> 	.prot =      &pingv6_prot,
> 	.ops =       &inet6_sockraw_ops,
> 	.flags =     INET_PROTOSW_REUSE,  <-- always makes `answer` NULL
> };
>
> int inet6_register_protosw(struct inet_protosw *p)
> {
> 	struct list_head *lh;
> 	struct inet_protosw *answer;
> 	struct list_head *last_perm;
> 	int protocol = p->protocol;
> 	int ret;
>
> 	spin_lock_bh(&inetsw6_lock);
>
> 	ret = -EINVAL;
> 	if (p->type >= SOCK_MAX)
> 		goto out_illegal;
>
> 	/* If we are trying to override a permanent protocol, bail. */
> 	answer = NULL;
> 	ret = -EPERM;
> 	last_perm = &inetsw6[p->type];
> 	list_for_each(lh, &inetsw6[p->type]) {
> 		answer = list_entry(lh, struct inet_protosw, list);
>
> 		/* Check only the non-wild match. */
> 		if (INET_PROTOSW_PERMANENT & answer->flags) {
> 			if (protocol == answer->protocol)
> 				break;
> 			last_perm = lh;
> 		}
>
> 		answer = NULL;
> 	}
> 	if (answer)
> 		goto out_permanent;
> ...
> 	list_add_rcu(&p->list, last_perm);
> 	ret = 0;
> out:
> 	spin_unlock_bh(&inetsw6_lock);
> 	return ret;
>
> out_permanent:
> 	pr_err("Attempt to override permanent protocol %d\n", protocol);
> 	goto out;
>
> out_illegal:
> 	pr_err("Ignoring attempt to register invalid socket type %d\n",
> 	       p->type);
> 	goto out;
> }
> ---8<---
>
>> This leaves wild ops in namespace list and when another module tries to
>> add or delete pernet namespace it triggers page fault.
>> Although IPv6 cannot be unloaded now, this error should still be handled
>> to avoid kernel panic during IPv6 initialization.
>>
>> BUG: unable to handle page fault for address: fffffbfff80bab69
>> CPU: 0 PID: 434 Comm: modprobe
>> RIP: 0010:unregister_pernet_operations+0xc9/0x450
>> Call Trace:
>>   <TASK>
>>   unregister_pernet_subsys+0x31/0x3e
>>   nf_tables_module_exit+0x44/0x6a [nf_tables]
>>   __do_sys_delete_module.constprop.0+0x34f/0x5b0
>>   ...
>>
>> Fix it by adding error handling in pingv6_init(), and add a helper
> I'm wondering this could be another place.
>
>
>> function pingv6_ops_unset to avoid duplicate code.
>>
>> Fixes: d862e5461423 ("net: ipv6: Implement /proc/net/icmp6.")
>> Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com>
>> ---
>>   net/ipv6/ping.c | 30 ++++++++++++++++++++++--------
>>   1 file changed, 22 insertions(+), 8 deletions(-)
>>
>> diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
>> index 86c26e48d065..5df688dd5208 100644
>> --- a/net/ipv6/ping.c
>> +++ b/net/ipv6/ping.c
>> @@ -277,10 +277,21 @@ static struct pernet_operations ping_v6_net_ops = {
>>   };
>>   #endif
>>   
>> +static void pingv6_ops_unset(void)
>> +{
>> +	pingv6_ops.ipv6_recv_error = dummy_ipv6_recv_error;
>> +	pingv6_ops.ip6_datagram_recv_common_ctl = dummy_ip6_datagram_recv_ctl;
>> +	pingv6_ops.ip6_datagram_recv_specific_ctl = dummy_ip6_datagram_recv_ctl;
>> +	pingv6_ops.icmpv6_err_convert = dummy_icmpv6_err_convert;
>> +	pingv6_ops.ipv6_icmp_error = dummy_ipv6_icmp_error;
>> +	pingv6_ops.ipv6_chk_addr = dummy_ipv6_chk_addr;
>> +}
>> +
>>   int __init pingv6_init(void)
>>   {
>> +	int ret;
>>   #ifdef CONFIG_PROC_FS
>> -	int ret = register_pernet_subsys(&ping_v6_net_ops);
>> +	ret = register_pernet_subsys(&ping_v6_net_ops);
>>   	if (ret)
>>   		return ret;
>>   #endif
>> @@ -291,7 +302,15 @@ int __init pingv6_init(void)
>>   	pingv6_ops.icmpv6_err_convert = icmpv6_err_convert;
>>   	pingv6_ops.ipv6_icmp_error = ipv6_icmp_error;
>>   	pingv6_ops.ipv6_chk_addr = ipv6_chk_addr;
>> -	return inet6_register_protosw(&pingv6_protosw);
>> +
>> +	ret = inet6_register_protosw(&pingv6_protosw);
>> +	if (ret) {
>> +		pingv6_ops_unset();
>> +#ifdef CONFIG_PROC_FS
>> +		unregister_pernet_subsys(&ping_v6_net_ops);
>> +#endif
>> +	}
>> +	return ret;
>>   }
>>   
>>   /* This never gets called because it's not possible to unload the ipv6 module,
>> @@ -299,12 +318,7 @@ int __init pingv6_init(void)
>>    */
>>   void pingv6_exit(void)
>>   {
>> -	pingv6_ops.ipv6_recv_error = dummy_ipv6_recv_error;
>> -	pingv6_ops.ip6_datagram_recv_common_ctl = dummy_ip6_datagram_recv_ctl;
>> -	pingv6_ops.ip6_datagram_recv_specific_ctl = dummy_ip6_datagram_recv_ctl;
>> -	pingv6_ops.icmpv6_err_convert = dummy_icmpv6_err_convert;
>> -	pingv6_ops.ipv6_icmp_error = dummy_ipv6_icmp_error;
>> -	pingv6_ops.ipv6_chk_addr = dummy_ipv6_chk_addr;
>> +	pingv6_ops_unset();
>>   #ifdef CONFIG_PROC_FS
>>   	unregister_pernet_subsys(&ping_v6_net_ops);
>>   #endif
>> -- 
>> 2.17.1
  

On Thu, Nov 3, 2022 at 6:36 PM Chen Zhongjin <chenzhongjin@huawei.com> wrote:
>
> Hi,
>
> On 2022/11/4 0:58, Kuniyuki Iwashima wrote:
> > From:   Chen Zhongjin <chenzhongjin@huawei.com>
> > Date:   Thu, 3 Nov 2022 17:03:45 +0800
> >> When IPv6 module initializing in pingv6_init(), inet6_register_protosw()
> >> is possible to fail but returns without any error cleanup.
> > The change itself looks sane, but how does it fail ?
> > It seems inet6_register_protosw() never fails for pingv6_protosw.
> > Am I missing something ?
>
> Thanks for reminding! I only injected error return value for functions
> but didn't notice the inner logic.
>
> Rechecked and find you are right that inet6_register_protosw() is safe
> for this case.
>
> Sorry for bothering, please reject this. Will check carefully next time.

This is silly and a waste of time for many of us.

If you want to send fixes for real bugs, I suggest you grab reports
from syzbot queues,
instead of 'injecting error values' from arbitrary functions.

Thanks.