Re: [PATCH net -v2] [BUGFIX] bonding: use local function pointer of bond->recv_probe in bond_handle_frame

Jay Vosburgh
2011-10-19T17:59:07Z

David Miller <davem@davemloft.net> wrote:

>From: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
>Date: Thu, 13 Oct 2011 11:04:29 +0900
>
>> The bond->recv_probe is called in bond_handle_frame() when
>> a packet is received, but bond_close() sets it to NULL. So,
>> a panic occurs when both functions work in parallel.
>>
>> Why this happen:
>> After null pointer check of bond->recv_probe, an sk_buff is
>> duplicated and bond->recv_probe is called in bond_handle_frame.
>> So, a panic occurs when bond_close() is called between the
>> check and call of bond->recv_probe.
>>
>> Patch:
>> This patch uses a local function pointer of bond->recv_probe
>> in bond_handle_frame(). So, it can avoid the null pointer
>> dereference.
>>
>>
>> Signed-off-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
>> Cc: Jay Vosburgh <fubar@us.ibm.com>
>> Cc: Andy Gospodarek <andy@greyhouse.net>
>> Cc: Eric Dumazet <eric.dumazet@gmail.com>
>> Cc: WANG Cong <xiyou.wangcong@gmail.com>
>
>Bonding folks please review this, thanks.
>

Looks reasonable. Even if by some quirk of timing the
recv_probe function ends up being entered after bond_close has
completed, it doesn't look like there is a risk of those functions
misbehaving (because bond_close doesn't deallocate the data structures).

-J

Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>

---
-Jay Vosburgh, IBM Linux Technology Center, fubar@us.ibm.com