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Date:   Fri, 22 Jun 2018 07:20:56 +0900 (KST)
Message-Id: <20180622.072056.1223319763674661318.davem@davemloft.net>
To:     garrmcnu@gmail.com
Cc:     netdev@vger.kernel.org, stephen@networkplumber.org,
        jiri@resnulli.us, nikolay@cumulusnetworks.com,
        bridge@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net: bridge: fix potential null pointer dereference on
 return from br_port_get_rtnl()
From:   David Miller <davem@davemloft.net>
In-Reply-To: <20180621201427.4961-1-garrmcnu@gmail.com>
References: <20180621201427.4961-1-garrmcnu@gmail.com>
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From: Garry McNulty <garrmcnu@gmail.com>
Date: Thu, 21 Jun 2018 21:14:27 +0100

> br_port_get_rtnl() can return NULL if the network device is not a bridge
> port (IFF_BRIDGE_PORT flag not set). br_port_slave_changelink() and
> br_port_fill_slave_info() callbacks dereference this pointer without
> checking. Currently this is not a problem because slave devices always
> set this flag. Add null check in case these conditions ever change.
> 
> Detected by CoverityScan, CID 1339613 ("Dereference null return value")
> 
> Signed-off-by: Garry McNulty <garrmcnu@gmail.com>

I don't think this is reasonable.

The bridge code will never, ever, install a slave that doesn't have
that bit set.  It's the most fundamental aspect of how these objects
are managed.