netdev - Re: [PATCH net] net: rtnetlink: prevent underflows in do

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Date:   Fri, 22 Nov 2019 07:21:22 +0000
From:   Parav Pandit <parav@...lanox.com>
To:     David Miller <davem@...emloft.net>,
        "dan.carpenter@...cle.com" <dan.carpenter@...cle.com>
CC:     Jiri Pirko <jiri@...lanox.com>,
        "dsahern@...il.com" <dsahern@...il.com>,
        Ido Schimmel <idosch@...lanox.com>,
        Petr Machata <petrm@...lanox.com>,
        "jakub.kicinski@...ronome.com" <jakub.kicinski@...ronome.com>,
        "nikolay@...ulusnetworks.com" <nikolay@...ulusnetworks.com>,
        "roopa@...ulusnetworks.com" <roopa@...ulusnetworks.com>,
        "johannes.berg@...el.com" <johannes.berg@...el.com>,
        "mkubecek@...e.cz" <mkubecek@...e.cz>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>
Subject: Re: [PATCH net] net: rtnetlink: prevent underflows in do_setvfinfo()

On 11/21/2019 4:44 PM, David Miller wrote:
> From: Dan Carpenter <dan.carpenter@...cle.com>
> Date: Wed, 20 Nov 2019 15:34:38 +0300
>
>> The "ivm->vf" variable is a u32, but the problem is that a number of
>> drivers cast it to an int and then forget to check for negatives.  An
>> example of this is in the cxgb4 driver.
>>
>> drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c
>>   2890  static int cxgb4_mgmt_get_vf_config(struct net_device *dev,
>>   2891                                      int vf, struct ifla_vf_info *ivi)
>>                                             ^^^^^^
>>   2892  {
>>   2893          struct port_info *pi = netdev_priv(dev);
>>   2894          struct adapter *adap = pi->adapter;
>>   2895          struct vf_info *vfinfo;
>>   2896  
>>   2897          if (vf >= adap->num_vfs)
>>                     ^^^^^^^^^^^^^^^^^^^
>>   2898                  return -EINVAL;
>>   2899          vfinfo = &adap->vfinfo[vf];
>>                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
>>
>> There are 48 functions affected.
>  ...
>> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> I'm going to apply this and queue it up for -stable.
>
> The u32 conversion should happen in next.
okay.
When Dan reported, I reviewed and wrote the patch for u32, and some more
code consolidation with it.
But hit the block with u32 leading to overflow to 0 which modifies the
first VF incorrectly.
Checking num_vfs of pci dev, without device_lock() is equally buggy as
it stands today.
Creating a lock in each vendor driver(s) doesn't make sense.
Haven't had chance yet after that.
Let me know if someone has a suggestion that I should incorporate.