[PATCH] cgroup: fix panic in netprio_cgroup

[PATCH] cgroup: fix panic in netprio_cgroup

[Gao feng]

we set max_prioidx to the first zero bit index of prioidx_map in
function get_prioidx.

So when we delete the low index netprio cgroup and adding a new
netprio cgroup again,the max_prioidx will be set to the low index.

when we set the high index cgroup's net_prio.ifpriomap,the function
write_priomap will call update_netdev_tables to alloc memory which
size is sizeof(struct netprio_map) + sizeof(u32) * (max_prioidx + 1),
so the size of array that map->priomap point to is max_prioidx +1,
which is low than what we actually need.

fix this by adding check in get_prioidx,only set max_prioidx when
max_prioidx low than the new prioidx.

Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
---
 net/core/netprio_cgroup.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index 5b8aa2f..586f7d9 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -50,7 +50,8 @@ static int get_prioidx(u32 *prio)
 	}
 	set_bit(prioidx, prioidx_map);
 	spin_unlock_irqrestore(&prioidx_map_lock, flags);
-	atomic_set(&max_prioidx, prioidx);
+	if (atomic_read(&max_prioidx) < prioidx)
+		atomic_set(&max_prioidx, prioidx);
 	*prio = prioidx;
 	return 0;
 }
-- 
1.7.7.6

Re: [PATCH] cgroup: fix panic in netprio_cgroup

[Eric Dumazet]

On Thu, 2012-07-05 at 16:31 +0800, Gao feng wrote:
> we set max_prioidx to the first zero bit index of prioidx_map in
> function get_prioidx.
> 
> So when we delete the low index netprio cgroup and adding a new
> netprio cgroup again,the max_prioidx will be set to the low index.
> 
> when we set the high index cgroup's net_prio.ifpriomap,the function
> write_priomap will call update_netdev_tables to alloc memory which
> size is sizeof(struct netprio_map) + sizeof(u32) * (max_prioidx + 1),
> so the size of array that map->priomap point to is max_prioidx +1,
> which is low than what we actually need.
> 
> fix this by adding check in get_prioidx,only set max_prioidx when
> max_prioidx low than the new prioidx.
> 
> Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
> ---
>  net/core/netprio_cgroup.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
> index 5b8aa2f..586f7d9 100644
> --- a/net/core/netprio_cgroup.c
> +++ b/net/core/netprio_cgroup.c
> @@ -50,7 +50,8 @@ static int get_prioidx(u32 *prio)
>  	}
>  	set_bit(prioidx, prioidx_map);
>  	spin_unlock_irqrestore(&prioidx_map_lock, flags);
> -	atomic_set(&max_prioidx, prioidx);
> +	if (atomic_read(&max_prioidx) < prioidx)
> +		atomic_set(&max_prioidx, prioidx);
>  	*prio = prioidx;
>  	return 0;
>  }

This is still racy.

Please do this before the 
spin_unlock_irqrestore(&prioidx_map_lock, flags);

Re: [PATCH] cgroup: fix panic in netprio_cgroup

[David Miller]

Why did you post this twice?

Is there a difference between the first patch and the second
one you posted?  If so, what is that difference?

Re: [PATCH] cgroup: fix panic in netprio_cgroup

[Gao feng]

于 2012年07月05日 16:43, Eric Dumazet 写道:
> On Thu, 2012-07-05 at 16:31 +0800, Gao feng wrote:
>> we set max_prioidx to the first zero bit index of prioidx_map in
>> function get_prioidx.
>>
>> So when we delete the low index netprio cgroup and adding a new
>> netprio cgroup again,the max_prioidx will be set to the low index.
>>
>> when we set the high index cgroup's net_prio.ifpriomap,the function
>> write_priomap will call update_netdev_tables to alloc memory which
>> size is sizeof(struct netprio_map) + sizeof(u32) * (max_prioidx + 1),
>> so the size of array that map->priomap point to is max_prioidx +1,
>> which is low than what we actually need.
>>
>> fix this by adding check in get_prioidx,only set max_prioidx when
>> max_prioidx low than the new prioidx.
>>
>> Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
>> ---
>>  net/core/netprio_cgroup.c |    3 ++-
>>  1 files changed, 2 insertions(+), 1 deletions(-)
>>
>> diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
>> index 5b8aa2f..586f7d9 100644
>> --- a/net/core/netprio_cgroup.c
>> +++ b/net/core/netprio_cgroup.c
>> @@ -50,7 +50,8 @@ static int get_prioidx(u32 *prio)
>>  	}
>>  	set_bit(prioidx, prioidx_map);
>>  	spin_unlock_irqrestore(&prioidx_map_lock, flags);
>> -	atomic_set(&max_prioidx, prioidx);
>> +	if (atomic_read(&max_prioidx) < prioidx)
>> +		atomic_set(&max_prioidx, prioidx);
>>  	*prio = prioidx;
>>  	return 0;
>>  }
> 
> This is still racy.
> 
> Please do this before the 
> spin_unlock_irqrestore(&prioidx_map_lock, flags);
> 

Thanks Eric,you are right
I will fix and resent it.

Re: [PATCH] cgroup: fix panic in netprio_cgroup

[Gao feng]

于 2012年07月05日 16:58, David Miller 写道:
> 
> Why did you post this twice?

Sorry to confuse you, there are something wrong with my git sendmail config.
I sent the first patch but I can't find it in the maillist,so I
sent it again.


> 
> Is there a difference between the first patch and the second
> one you posted?  If so, what is that difference?

there isn't a difference between them.
Sorry again.

Thanks.