[PATCH net] ipmr: tune the ipmr_can_free_table() checks.

[PATCH net] ipmr: tune the ipmr_can_free_table() checks.

[Paolo Abeni]

Eric reported a syzkaller-triggered splat caused by recent ipmr changes:

WARNING: CPU: 2 PID: 6041 at net/ipv6/ip6mr.c:419
ip6mr_free_table+0xbd/0x120 net/ipv6/ip6mr.c:419
Modules linked in:
CPU: 2 UID: 0 PID: 6041 Comm: syz-executor183 Not tainted
6.12.0-syzkaller-10681-g65ae975e97d5 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:ip6mr_free_table+0xbd/0x120 net/ipv6/ip6mr.c:419
Code: 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c
02 00 75 58 49 83 bc 24 c0 0e 00 00 00 74 09 e8 44 ef a9 f7 90 <0f> 0b
90 e8 3b ef a9 f7 48 8d 7b 38 e8 12 a3 96 f7 48 89 df be 0f
RSP: 0018:ffffc90004267bd8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff88803c710000 RCX: ffffffff89e4d844
RDX: ffff88803c52c880 RSI: ffffffff89e4d87c RDI: ffff88803c578ec0
RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: ffff88803c578000
R13: ffff88803c710000 R14: ffff88803c710008 R15: dead000000000100
FS: 00007f7a855ee6c0(0000) GS:ffff88806a800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7a85689938 CR3: 000000003c492000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
ip6mr_rules_exit+0x176/0x2d0 net/ipv6/ip6mr.c:283
ip6mr_net_exit_batch+0x53/0xa0 net/ipv6/ip6mr.c:1388
ops_exit_list+0x128/0x180 net/core/net_namespace.c:177
setup_net+0x4fe/0x860 net/core/net_namespace.c:394
copy_net_ns+0x2b4/0x6b0 net/core/net_namespace.c:500
create_new_namespaces+0x3ea/0xad0 kernel/nsproxy.c:110
unshare_nsproxy_namespaces+0xc0/0x1f0 kernel/nsproxy.c:228
ksys_unshare+0x45d/0xa40 kernel/fork.c:3334
__do_sys_unshare kernel/fork.c:3405 [inline]
__se_sys_unshare kernel/fork.c:3403 [inline]
__x64_sys_unshare+0x31/0x40 kernel/fork.c:3403
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7a856332d9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 18 00 00 90 48 89 f8 48
89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d
01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7a855ee238 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007f7a856bd308 RCX: 00007f7a856332d9
RDX: 00007f7a8560f8c6 RSI: 0000000000000000 RDI: 0000000062040200
RBP: 00007f7a856bd300 R08: 00007fff932160a7 R09: 00007f7a855ee6c0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f7a856bd30c
R13: 0000000000000000 R14: 00007fff93215fc0 R15: 00007fff932160a8
</TASK>

The root cause is a network namespace creation failing after successful
initialization of the ipmr subsystem. Such a case is not currently
matched by the ipmr_can_free_table() helper.

New namespaces are zeroed on allocation and inserted into net ns list
only after successful creation; when deleting an ipmr table, the list
next pointer can be NULL only on netns initialization failure.

Update the ipmr_can_free_table() checks leveraging such condition.

Reported-by: Eric Dumazet <edumazet@google.com>
Fixes: 11b6e701bce9 ("ipmr: add debug check for mr table cleanup")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 net/ipv4/ipmr.c  | 2 +-
 net/ipv6/ip6mr.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index c5b8ec5c0a8c..d814a352cc05 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -122,7 +122,7 @@ static void ipmr_expire_process(struct timer_list *t);
 
 static bool ipmr_can_free_table(struct net *net)
 {
-	return !check_net(net) || !net->ipv4.mr_rules_ops;
+	return !check_net(net) || !net->list.next;
 }
 
 static struct mr_table *ipmr_mr_table_iter(struct net *net,
diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 7f1902ac3586..37224a5f1bbe 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -110,7 +110,7 @@ static void ipmr_expire_process(struct timer_list *t);
 
 static bool ip6mr_can_free_table(struct net *net)
 {
-	return !check_net(net) || !net->ipv6.mr6_rules_ops;
+	return !check_net(net) || !net->list.next;
 }
 
 static struct mr_table *ip6mr_mr_table_iter(struct net *net,
-- 
2.45.2

Re: [PATCH net] ipmr: tune the ipmr_can_free_table() checks.

[David Ahern]

On 11/29/24 3:23 AM, Paolo Abeni wrote:
> diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
> index c5b8ec5c0a8c..d814a352cc05 100644
> --- a/net/ipv4/ipmr.c
> +++ b/net/ipv4/ipmr.c
> @@ -122,7 +122,7 @@ static void ipmr_expire_process(struct timer_list *t);
>  
>  static bool ipmr_can_free_table(struct net *net)
>  {
> -	return !check_net(net) || !net->ipv4.mr_rules_ops;
> +	return !check_net(net) || !net->list.next;
>  }
>  
>  static struct mr_table *ipmr_mr_table_iter(struct net *net,
> diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
> index 7f1902ac3586..37224a5f1bbe 100644
> --- a/net/ipv6/ip6mr.c
> +++ b/net/ipv6/ip6mr.c
> @@ -110,7 +110,7 @@ static void ipmr_expire_process(struct timer_list *t);
>  
>  static bool ip6mr_can_free_table(struct net *net)
>  {
> -	return !check_net(net) || !net->ipv6.mr6_rules_ops;
> +	return !check_net(net) || !net->list.next;
>  }
>  
>  static struct mr_table *ip6mr_mr_table_iter(struct net *net,

this exposes internal namespace details to ipmr code. How about a helper
in net_namespace.h that indicates the intent here?

Re: [PATCH net] ipmr: tune the ipmr_can_free_table() checks.

[Paolo Abeni]

On 11/29/24 18:01, David Ahern wrote:
> On 11/29/24 3:23 AM, Paolo Abeni wrote:
>> diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
>> index c5b8ec5c0a8c..d814a352cc05 100644
>> --- a/net/ipv4/ipmr.c
>> +++ b/net/ipv4/ipmr.c
>> @@ -122,7 +122,7 @@ static void ipmr_expire_process(struct timer_list *t);
>>  
>>  static bool ipmr_can_free_table(struct net *net)
>>  {
>> -	return !check_net(net) || !net->ipv4.mr_rules_ops;
>> +	return !check_net(net) || !net->list.next;
>>  }
>>  
>>  static struct mr_table *ipmr_mr_table_iter(struct net *net,
>> diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
>> index 7f1902ac3586..37224a5f1bbe 100644
>> --- a/net/ipv6/ip6mr.c
>> +++ b/net/ipv6/ip6mr.c
>> @@ -110,7 +110,7 @@ static void ipmr_expire_process(struct timer_list *t);
>>  
>>  static bool ip6mr_can_free_table(struct net *net)
>>  {
>> -	return !check_net(net) || !net->ipv6.mr6_rules_ops;
>> +	return !check_net(net) || !net->list.next;
>>  }
>>  
>>  static struct mr_table *ip6mr_mr_table_iter(struct net *net,
> 
> this exposes internal namespace details to ipmr code. How about a helper
> in net_namespace.h that indicates the intent here?

Makes sense. What about something alike:

static bool net_setup_completed(struct net *net)
{
	return net->list.next;
}

in net_namespace.h?

The question is mainly about the name, which I'm notably bad to pick.

Thanks,

Paolo

Re: [PATCH net] ipmr: tune the ipmr_can_free_table() checks.

[Paolo Abeni]

On 11/29/24 18:13, Paolo Abeni wrote:
> On 11/29/24 18:01, David Ahern wrote:
>> On 11/29/24 3:23 AM, Paolo Abeni wrote:
>>> diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
>>> index c5b8ec5c0a8c..d814a352cc05 100644
>>> --- a/net/ipv4/ipmr.c
>>> +++ b/net/ipv4/ipmr.c
>>> @@ -122,7 +122,7 @@ static void ipmr_expire_process(struct timer_list *t);
>>>  
>>>  static bool ipmr_can_free_table(struct net *net)
>>>  {
>>> -	return !check_net(net) || !net->ipv4.mr_rules_ops;
>>> +	return !check_net(net) || !net->list.next;
>>>  }
>>>  
>>>  static struct mr_table *ipmr_mr_table_iter(struct net *net,
>>> diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
>>> index 7f1902ac3586..37224a5f1bbe 100644
>>> --- a/net/ipv6/ip6mr.c
>>> +++ b/net/ipv6/ip6mr.c
>>> @@ -110,7 +110,7 @@ static void ipmr_expire_process(struct timer_list *t);
>>>  
>>>  static bool ip6mr_can_free_table(struct net *net)
>>>  {
>>> -	return !check_net(net) || !net->ipv6.mr6_rules_ops;
>>> +	return !check_net(net) || !net->list.next;
>>>  }
>>>  
>>>  static struct mr_table *ip6mr_mr_table_iter(struct net *net,
>>
>> this exposes internal namespace details to ipmr code. How about a helper
>> in net_namespace.h that indicates the intent here?
> 
> Makes sense. What about something alike:
> 
> static bool net_setup_completed(struct net *net)
> {
> 	return net->list.next;
> }
> 
> in net_namespace.h?
> 
> The question is mainly about the name, which I'm notably bad to pick.

Thinking again about it, I would use 'net_initialized', unless someone
has a better option.

Thanks,

Paolo

Re: [PATCH net] ipmr: tune the ipmr_can_free_table() checks.

[David Ahern]

On 11/29/24 11:02 AM, Paolo Abeni wrote:
> Thinking again about it, I would use 'net_initialized', unless someone
> has a better option.

works for me.