Re: [PATCH] net: mac80211: cfg: enforce sanity checks for key_index in ieee80211_del_key()

[Johannes Berg]

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