linux-kernel - Re: [PATCH] tipc: ensure skb->lock is initialised

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Message-ID: <87fd2150548041219fc42bce80b63c9c@svr-chch-ex1.atlnz.lc>
Date:   Mon, 8 Jul 2019 21:13:45 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        "jon.maloy@...csson.com" <jon.maloy@...csson.com>,
        "ying.xue@...driver.com" <ying.xue@...driver.com>,
        "davem@...emloft.net" <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "tipc-discussion@...ts.sourceforge.net" 
        <tipc-discussion@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tipc: ensure skb->lock is initialised

On 9/07/19 8:43 AM, Chris Packham wrote:
> On 8/07/19 8:18 PM, Eric Dumazet wrote:
>>
>>
>> On 7/8/19 12:53 AM, Chris Packham wrote:
>>> tipc_named_node_up() creates a skb list. It passes the list to
>>> tipc_node_xmit() which has some code paths that can call
>>> skb_queue_purge() which relies on the list->lock being initialised.
>>> Ensure tipc_named_node_up() uses skb_queue_head_init() so that the lock
>>> is explicitly initialised.
>>>
>>> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
>>
>> I would rather change the faulty skb_queue_purge() to __skb_queue_purge()
>>
> 
> Makes sense. I'll look at that for v2.
> 

Actually maybe not. tipc_rcast_xmit(), tipc_node_xmit_skb(), 
tipc_send_group_msg(), __tipc_sendmsg(), __tipc_sendstream(), and 
tipc_sk_timeout() all use skb_queue_head_init(). So my original change 
brings tipc_named_node_up() into line with them.

I think it should be safe for tipc_node_xmit() to use 
__skb_queue_purge() since all the callers seem to have exclusive access 
to the list of skbs. It still seems that the callers should all use 
skb_queue_head_init() for consistency.