netdev - Re: [PATCH] ethtool: fix a missing-check bug

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Message-Id: <20181015.213928.1979135633281436819.davem@davemloft.net>
Date:   Mon, 15 Oct 2018 21:39:28 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     wang6495@....edu
Cc:     kjlu@....edu, f.fainelli@...il.com, keescook@...omium.org,
        ilyal@...lanox.com, ecree@...arflare.com,
        ynorov@...iumnetworks.com, alan.brady@...el.com,
        eugenia@...lanox.com, stephen@...workplumber.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ethtool: fix a missing-check bug

From: Wenwen Wang <wang6495@....edu>
Date: Tue,  9 Oct 2018 08:15:38 -0500

> In ethtool_get_rxnfc(), the eth command 'cmd' is compared against
> 'ETHTOOL_GRXFH' to see whether it is necessary to adjust the variable
> 'info_size'. Then the whole structure of 'info' is copied from the
> user-space buffer 'useraddr' with 'info_size' bytes. In the following
> execution, 'info' may be copied again from the buffer 'useraddr' depending
> on the 'cmd' and the 'info.flow_type'. However, after these two copies,
> there is no check between 'cmd' and 'info.cmd'. In fact, 'cmd' is also
> copied from the buffer 'useraddr' in dev_ethtool(), which is the caller
> function of ethtool_get_rxnfc(). Given that 'useraddr' is in the user
> space, a malicious user can race to change the eth command in the buffer
> between these copies. By doing so, the attacker can supply inconsistent
> data and cause undefined behavior because in the following execution 'info'
> will be passed to ops->get_rxnfc().
> 
> This patch adds a necessary check on 'info.cmd' and 'cmd' to confirm that
> they are still same after the two copies in ethtool_get_rxnfc(). Otherwise,
> an error code EINVAL will be returned.
> 
> Signed-off-by: Wenwen Wang <wang6495@....edu>

Applied.