linux-kernel - Re: [PATCH v3] net: cgroup: fix access the unallocated memory in netprio cgroup

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Date:	Wed, 11 Jul 2012 20:51:42 +0800
From:	Gao feng <gaofeng@...fujitsu.com>
To:	Neil Horman <nhorman@...driver.com>
CC:	eric.dumazet@...il.com, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, lizefan@...wei.com, tj@...nel.org,
	davem@...emloft.net, Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH v3] net: cgroup: fix access the unallocated memory in
 netprio cgroup

于 2012年07月11日 20:11, Neil Horman 写道:
> On Wed, Jul 11, 2012 at 04:30:06PM +0800, Gao feng wrote:
>> there are some out of bound accesses in netprio cgroup.
>>
>> now before accessing the dev->priomap.priomap array,we only check
>> if the dev->priomap exist.and because we don't want to see
>> additional bound checkings in fast path, so we should make sure
>> that dev->priomap is null or array size of dev->priomap.priomap
>> is equal to max_prioidx + 1;
>>
>> and it's not needed to call extend_netdev_tabel in write_priomap,
>> we can only allocate the net device's priomap which we change through
>> net_prio.ifpriomap.
>>
>> this patch add a return value for update_netdev_tables & extend_netdev_table,
>> so when new_priomap is allocated failed,write_priomap will stop to access
>> the priomap,and return -ENOMEM back to the userspace to tell the user
>> what happend.
>>
>> Change From v2:
>> 1. protect extend_netdev_table by RTNL.
>> 2. when extend_netdev_table failed,call dev_put to reduce device's refcount.
>>
>> Signed-off-by: Gao feng <gaofeng@...fujitsu.com>
>> Cc: Neil Horman <nhorman@...driver.com>
>> Cc: Eric Dumazet <edumazet@...gle.com>
>> ---
>>  net/core/netprio_cgroup.c |   54 ++++++++++++++++++++++++++++++++------------
>>  1 files changed, 39 insertions(+), 15 deletions(-)
>>
> I still think the use of max_priomap in write_priomap is racy (please see my
> previous note).
> 
> Neil

Yes, you are right :(
we need a v4 patch.

Thanks!
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