On 01/12/20 5:36 pm, Johannes Berg wrote: > On Tue, 2020-12-01 at 17:26 +0530, Anant Thazhemadam wrote: >> On 01/12/20 3:30 pm, Johannes Berg wrote: >>> 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. >> Hello, >> >> This gave me the idea of trying to use cfg80211_validate_key_settings() >> directly in ieee80211_del_key(). I did try that out, tested it, and this bug >> doesn't seem to be getting triggered anymore. >> If this is okay, then I can send in a v2 soon. :) >> >> If there is any reason that I'm missing as to why cfg80211_validate_key_settings() >> cannot be used in this context, please let me know. > If it works then I guess that's OK. I thought we didn't have all the > right information, e.g. whether a key is pairwise or not? > > johannes > Well, cfg80211_supported_cipher_suite(&rdev->wiphy, params->cipher) returned false, and thus it worked for the syzbot reproducer. Would it be a safer idea to enforce the conditions that I initially put (in ieee80211_del_key()) directly in cfg80211_validate_key_settings() itself - by updating max_key_index, and checking accordingly? Thanks, Anant
