netdev - Re: [PATCH] ppp: fix segfaults introduced by netdev

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Message-ID: <494A24EB.8020307@katalix.com>
Date:	Thu, 18 Dec 2008 10:24:43 +0000
From:	James Chapman <jchapman@...alix.com>
To:	Wang Chen <wangchen@...fujitsu.com>
CC:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] ppp: fix segfaults introduced by netdev_priv changes

Wang Chen wrote:

> I have no comment on these changes, but
> there is a path that calls only ppp_destroy_interface() no
> ppp_shutdown_interface().
> it's:
> ppp_unregister_channel
>     --->ppp_disconnect_channel()
>         ---> ppp_destroy_interface()

Isn't ppp_shutdown_interface() always called first? If not, then we need
to unregister_netdev() before the free_netdev() call in
ppp_destroy_interface(). The original code didn't cover that case.

>>  /*
>> @@ -2616,7 +2614,7 @@ ppp_connect_channel(struct channel *pch, int unit)
>>  	if (pch->file.hdrlen > ppp->file.hdrlen)
>>  		ppp->file.hdrlen = pch->file.hdrlen;
>>  	hdrlen = pch->file.hdrlen + 2;	/* for protocol bytes */
>> -	if (ppp->dev && hdrlen > ppp->dev->hard_header_len)
>> +	if (hdrlen > ppp->dev->hard_header_len)
>>  		ppp->dev->hard_header_len = hdrlen;
>>  	list_add_tail(&pch->clist, &ppp->channels);
>>  	++ppp->n_channels;
> 
> I don't understand this change.
> Do you mean that in this place, ppp->dev will never be NULL?

After my change, yes. See the comment in the patch preamble.

-- 
James Chapman
Katalix Systems Ltd
http://www.katalix.com
Catalysts for your Embedded Linux software development

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