linux-kernel - Re: [PATCH] net: bridge: fix potential null pointer dereference on return from br_port_get

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Date:   Fri, 22 Jun 2018 07:20:56 +0900 (KST)
From:   David Miller <davem@...emloft.net>
To:     garrmcnu@...il.com
Cc:     netdev@...r.kernel.org, stephen@...workplumber.org,
        jiri@...nulli.us, nikolay@...ulusnetworks.com,
        bridge@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: bridge: fix potential null pointer dereference on
 return from br_port_get_rtnl()

From: Garry McNulty <garrmcnu@...il.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@...il.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.