netdev - Re: [PATCH net-next] netlink: make getters tolerate NULL nla arg

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Message-Id: <20200117.040849.2032549448991143345.davem@davemloft.net>
Date:   Fri, 17 Jan 2020 04:08:49 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     fw@...len.de
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next] netlink: make getters tolerate NULL nla arg

From: Florian Westphal <fw@...len.de>
Date: Thu, 16 Jan 2020 15:55:22 +0100

> One recurring bug pattern triggered by syzbot is NULL dereference in
> netlink code paths due to a missing "tb[NL_ARG_FOO] != NULL" test.
> 
> At least some of these missing checks would not have crashed the kernel if
> the various nla_get_XXX helpers would return 0 in case of missing arg.
> 
> Make the helpers return 0 instead of crashing when a null nla is provided.
> Even with allyesconfig the .text increase is only about 350 bytes.
> 
> Signed-off-by: Florian Westphal <fw@...len.de>

Sorry, I think it's better to find out when code is trying to access
attributes without verifying that they are even supplied.