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

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Message-ID: <20120711121102.GB26643@hmsreliant.think-freely.org>
Date:	Wed, 11 Jul 2012 08:11:02 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Gao feng <gaofeng@...fujitsu.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

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

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