netdev - Re: [PATCH net-next] nfnetlink_queue: enable PID info retrieval

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Date:	Fri, 10 Jun 2016 00:21:41 +0200
From:	Daniel Borkmann <daniel@...earbox.net>
To:	Florian Westphal <fw@...len.de>,
	Saeed Mahameed <saeedm@...lanox.com>
CC:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org,
	Yevgeny Petrilin <yevgenyp@...lanox.com>,
	Andre Melkoumian <andre@...lanox.com>,
	Matthew Finlay <matt@...lanox.com>,
	Pablo Neira Ayuso <pablo@...filter.org>,
	Patrick McHardy <kaber@...sh.net>,
	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>
Subject: Re: [PATCH net-next] nfnetlink_queue: enable PID info retrieval

On 06/09/2016 11:35 PM, Florian Westphal wrote:
> Saeed Mahameed <saeedm@...lanox.com> wrote:
>> index a1bd161..67de200 100644
>> --- a/net/socket.c
>> +++ b/net/socket.c
>> @@ -382,6 +382,7 @@ struct file *sock_alloc_file(struct socket *sock, int flags, const char *dname)
>>   	}
>>
>>   	sock->file = file;
>> +	file->f_owner.sock_pid  = find_get_pid(task_pid_nr(current));
>>   	file->f_flags = O_RDWR | (flags & O_NONBLOCK);
>>   	file->private_data = sock;
>>   	return file;
>
> This looks like this leaks sock_pid reference...?
>
> (find_get_pid -> get_pid -> atomic_inc() , I don't see a put_pid in the
>   patch)
>
> Can't comment further than this since I'm not familiar with vfs; e.g.
> I can't say if fown_struct is right place or not, or if this approach
> even works when creating process has exited after fork, etc.

Or ... if you xmit the fd via unix domain socket to a different process
and initial owner terminates, which should give you invalid information
then; afaik, this would just increase struct file's refcnt and hand out
an unused fdnum ( get_unused_fd_flags() + fd_install(), etc).
For extending 'struct fown_struct', you probably also need to Cc fs folks.