linux-kernel - Re: [PATCH 2/2] airo: Add missing CAP_NET_ADMIN check in AIROOLDIOCTL/SIOCDEVPRIVATE

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Date:   Thu, 23 Jan 2020 11:03:59 +0100 (CET)
From:   David Miller <davem@...emloft.net>
To:     mpe@...erman.id.au
Cc:     netdev@...r.kernel.org, linux-wireless@...r.kernel.org,
        kvalo@...eaurora.org, linux-kernel@...r.kernel.org,
        security@...nel.org, ivansprundel@...ctive.com
Subject: Re: [PATCH 2/2] airo: Add missing CAP_NET_ADMIN check in
 AIROOLDIOCTL/SIOCDEVPRIVATE

From: Michael Ellerman <mpe@...erman.id.au>
Date: Wed, 22 Jan 2020 15:07:28 +1100

> The driver for Cisco Aironet 4500 and 4800 series cards (airo.c),
> implements AIROOLDIOCTL/SIOCDEVPRIVATE in airo_ioctl().
> 
> The ioctl handler copies an aironet_ioctl struct from userspace, which
> includes a command. Some of the commands are handled in readrids(),
> where the user controlled command is converted into a driver-internal
> value called "ridcode".
> 
> There are two command values, AIROGWEPKTMP and AIROGWEPKNV, which
> correspond to ridcode values of RID_WEP_TEMP and RID_WEP_PERM
> respectively. These commands both have checks that the user has
> CAP_NET_ADMIN, with the comment that "Only super-user can read WEP
> keys", otherwise they return -EPERM.
> 
> However there is another command value, AIRORRID, that lets the user
> specify the ridcode value directly, with no other checks. This means
> the user can bypass the CAP_NET_ADMIN check on AIROGWEPKTMP and
> AIROGWEPKNV.
> 
> Fix it by moving the CAP_NET_ADMIN check out of the command handling
> and instead do it later based on the ridcode. That way regardless of
> whether the ridcode is set via AIROGWEPKTMP or AIROGWEPKNV, or passed
> in using AIRORID, we always do the CAP_NET_ADMIN check.
> 
> Found by Ilja by code inspection, not tested as I don't have the
> required hardware.
> 
> Reported-by: Ilja Van Sprundel <ivansprundel@...ctive.com>
> Signed-off-by: Michael Ellerman <mpe@...erman.id.au>

Applied and queued up for -stable.