netdev - Re: [PATCH net-next] scm: Don't use struct ucred in NETLINK_CB and struct scm

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Message-Id: <20120907.144250.592587303760599718.davem@davemloft.net>
Date:	Fri, 07 Sep 2012 14:42:50 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	ebiederm@...ssion.com
Cc:	netdev@...r.kernel.org, serge@...lyn.com, eric.dumazet@...il.com
Subject: Re: [PATCH net-next] scm: Don't use struct ucred in NETLINK_CB and
 struct scm_cookie.

From: ebiederm@...ssion.com (Eric W. Biederman)
Date: Thu, 06 Sep 2012 21:20:01 -0700

> 
> Passing uids and gids on NETLINK_CB from a process in one user
> namespace to a process in another user namespace can result in the
> wrong uid or gid being presented to userspace.  Avoid that problem by
> passing kuids and kgids instead.
> 
> - define struct scm_creds for use in scm_cookie and netlink_skb_parms
>   that holds uid and gid information in kuid_t and kgid_t.
> 
> - Modify scm_set_cred to fill out scm_creds by heand instead of using
>   cred_to_ucred to fill out struct ucred.  This conversion ensures
>   userspace does not get incorrect uid or gid values to look at.
> 
> - Modify scm_recv to convert from struct scm_creds to struct ucred
>   before copying credential values to userspace.
> 
> - Modify __scm_send to populate struct scm_creds on in the scm_cookie,
>   instead of just copying struct ucred from userspace.
> 
> - Modify netlink_sendmsg to copy scm_creds instead of struct ucred
>   into the NETLINK_CB.
> 
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>

Applied, thanks Eric.
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