netdev - Re: [RFC 2/2] net: Allow protocols to provide an unlocked_recvmsg sk

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Date:	Fri, 22 May 2009 00:47:38 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	remi.denis-courmont@...ia.com
Cc:	acme@...hat.com, netdev@...r.kernel.org, vanhoof@...hat.com,
	williams@...hat.com
Subject: Re: [RFC 2/2] net: Allow protocols to provide an unlocked_recvmsg
 sk_prot method

From: "Rémi Denis-Courmont" <remi.denis-courmont@...ia.com>
Date: Fri, 22 May 2009 10:26:51 +0300

> On Thursday 21 May 2009 02:06:59 ext Arnaldo Carvalho de Melo wrote:
>> @@ -265,6 +265,9 @@ struct ucred {
>>  #define MSG_ERRQUEUE	0x2000	/* Fetch message from error queue */
>>  #define MSG_NOSIGNAL	0x4000	/* Do not generate SIGPIPE */
>>  #define MSG_MORE	0x8000	/* Sender will send more */
>> +#ifdef __KERNEL__
>> +#define MSG_UNLOCKED	0x10000	/* Don't lock the sock */
>> +#endif
> 
> I might be missing something but... What prevents an evil userland from 
> setting the flag anyway and hitting the BUG case?

Yes, we'll need to clear this on all paths where we get msg
flags from the user.

There's a lot of such places.

So maybe we need to pass this state around in a different,
internal, way.
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