netdev - Re: [PATCH net] net: dcb: Validate netlink message in DCB handler

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Message-ID: <20201223122211.31b8f3c4@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 23 Dec 2020 12:22:11 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Petr Machata <me@...chata.org>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Alexander Duyck <alexander.h.duyck@...el.com>,
        Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: Re: [PATCH net] net: dcb: Validate netlink message in DCB handler

On Tue, 22 Dec 2020 22:49:44 +0100 Petr Machata wrote:
> DCB uses the same handler function for both RTM_GETDCB and RTM_SETDCB
> messages. dcb_doit() bounces RTM_SETDCB mesasges if the user does not have
> the CAP_NET_ADMIN capability.
> 
> However, the operation to be performed is not decided from the DCB message
> type, but from the DCB command. Thus DCB_CMD_*_GET commands are used for
> reading DCB objects, the corresponding SET and DEL commands are used for
> manipulation.
> 
> The assumption is that set-like commands will be sent via an RTM_SETDCB
> message, and get-like ones via RTM_GETDCB. However, this assumption is not
> enforced.
> 
> It is therefore possible to manipulate DCB objects without CAP_NET_ADMIN
> capability by sending the corresponding command in an RTM_GETDCB message.
> That is a bug. Fix it by validating the type of the request message against
> the type used for the response.
> 
> Fixes: 2f90b8657ec9 ("ixgbe: this patch adds support for DCB to the kernel and ixgbe driver")
> Signed-off-by: Petr Machata <me@...chata.org>

Applied, thanks!