linux-kernel - Re: [PATCH] net: mac80211: cfg: enforce sanity checks for key_index in ieee80211_del

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Message-ID: <3025db173074d4dfbc323e91d3586f0e36426cf0.camel@sipsolutions.net>
Date:   Tue, 01 Dec 2020 11:00:37 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     Anant Thazhemadam <anant.thazhemadam@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        syzbot+49d4cab497c2142ee170@...kaller.appspotmail.com
Subject: Re: [PATCH] net: mac80211: cfg: enforce sanity checks for key_index
 in ieee80211_del_key()

On Tue, 2020-12-01 at 15:26 +0530, Anant Thazhemadam wrote:
> Currently, it is assumed that key_idx values that are passed to
> ieee80211_del_key() are all valid indexes as is, and no sanity checks
> are performed for it.
> However, syzbot was able to trigger an array-index-out-of-bounds bug
> by passing a key_idx value of 5, when the maximum permissible index
> value is (NUM_DEFAULT_KEYS - 1).
> Enforcing sanity checks helps in preventing this bug, or a similar
> instance in the context of ieee80211_del_key() from occurring.

I think we should do this more generally in cfg80211, like in
nl80211_new_key() we do it via cfg80211_validate_key_settings().

I suppose we cannot use the same function, but still, would be good to
address this generally in nl80211 for all drivers.

johannes