Hi Arend, >>>>>>>> i was able to reproduce an (maybe older issue) with 4-way handshake >>>>>>>> offloading for 802.1X in the brcmfmac driver. My setup consists of >>>>>>>> Raspberry Pi 3 B (current linux-next, arm64/defconfig) on STA side and >>>>>>>> a >>>>>>>> Raspberry Pi 3 A+ (Linux 4.19) on AP side. >>>>>>> >>>>>>> Looks like Raspberry Pi isn't the only affected platform [3], [4]. >>>>>>> >>>>>>> [3] - https://bugzilla.redhat.com/show_bug.cgi?id=1665608 >>>>>>> [4] - https://bugzilla.kernel.org/show_bug.cgi?id=202521 >>>>>> >>>>>> Stefan, >>>>>> >>>>>> Could you please try the attached patch for your wpa_supplicant? We'll >>>>>> upstream if it works for you. >>>>> >>>>> I hope that someone is also providing a kernel patch to fix the issue. >>>>> Hacking around a kernel issue in userspace is not enough. Fix the root >>>>> cause in the kernel. >>>> Marcel, >>>> This is a kernel warning for invalid application PMK set actions, so the >>>> fix is to only set PMK to wifi driver when 4-way is offloaded. I think >>>> Arend added the WARN_ON() intentionally to catch application misuse of >>>> PMK setting. >>>> You may also remove the warnings with the attached patch, but let's see >>>> what Arend says first. >>>> Arend, >>>> Any comment? >>> >>> Hi Chi-Hsien, Marcel >>> >>> From the kernel side I do not see an issue. In order to use 802.1X offload >>> the NL80211_ATTR_WANT_1X_4WAY_HS flag must be set in NL80211_CMD_CONNECT. >>> Otherwise, NL80211_CMD_SET_PMK is not accepted. The only improvement would >>> be to document this more clearly in the "WPA/WPA2 EAPOL handshake offload" >>> DOC section in nl80211.h. >> so nl80211 is an API. And an application can use that API wrongly (be that >> intentionally or unintentionally), the kernel can not just go WARN_ON and >> print a backtrace. That is your bug. So please handle wrong user input >> properly. > > You are right. However, the kernel does also return an error if the WARN_ON > is hit. We can improve by using the EXT_ACK functionality to provide more > info than just -EINVAL, eg. "PMK not accepted; no 802.1X offload requested on > connect”.
just remove the WARN_ON and replace it with a dev_warn. Userspace should not be able to trigger WARN_ON by using nl80211. >> Frankly, I don’t get why nl80211 itself is not validating the input and this >> is left to the driver. I think we need a nl80211 fuzzer that really >> exercises this API with random values and parameters to provide invalid >> input. > > That would mean nl80211 should keep state info between commands. From what I > remember that has been avoided from day one because of the experiences with > that in the WEXT days. I welcome any testing be it fuzzer or something else. And now driver bugs are bleeding into the API. I expect from a kernel API that it hides driver details. From an userspace program perspective I expect exactly the same input validation and behavior no matter what hardware is used underneath. If we can not do that, then this API has a broken design. Regards Marcel
