From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 25F46C2BA19 for ; Mon, 6 Apr 2020 13:27:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E9F312312F for ; Mon, 6 Apr 2020 13:27:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="vHsrIhjY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728405AbgDFN1Y (ORCPT ); Mon, 6 Apr 2020 09:27:24 -0400 Received: from mail27.static.mailgun.info ([104.130.122.27]:18215 "EHLO mail27.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728193AbgDFN1X (ORCPT ); Mon, 6 Apr 2020 09:27:23 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1586179642; h=Content-Type: MIME-Version: Message-ID: In-Reply-To: Date: References: Subject: Cc: To: From: Sender; bh=sg0YR1A5Pef3VRnFaQiwEzT6F8DEIg+uQHeuwoU6nms=; b=vHsrIhjYN63wFKbB0GJxOfG18aUbWk2JB1UZtLxcf0M3rAjhgK9zomhHQGC5QP9BQ5532lyK xmkwKIpQq6auuGM+fRDXl6ZiSBmmmDghJkJRRPBgOgorv2jHehG/1QQxZwesfawPkaBtGp8U CuXx3VfBI1rPl7PH6nFcvMhNHfY= X-Mailgun-Sending-Ip: 104.130.122.27 X-Mailgun-Sid: WyJiZjI2MiIsICJuZXRkZXZAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by mxa.mailgun.org with ESMTP id 5e8b2e2b.7fc892fc7f80-smtp-out-n02; Mon, 06 Apr 2020 13:27:07 -0000 (UTC) Received: by smtp.codeaurora.org (Postfix, from userid 1001) id A120AC44788; Mon, 6 Apr 2020 13:27:06 +0000 (UTC) Received: from potku.adurom.net (88-114-240-156.elisa-laajakaista.fi [88.114.240.156]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: kvalo) by smtp.codeaurora.org (Postfix) with ESMTPSA id DF11EC433BA; Mon, 6 Apr 2020 13:27:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org DF11EC433BA Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=none smtp.mailfrom=kvalo@codeaurora.org From: Kalle Valo To: Sumit Garg Cc: Johannes Berg , linux-wireless@vger.kernel.org, "David S. Miller" , kuba@kernel.org, netdev@vger.kernel.org, Linux Kernel Mailing List , Matthias-Peter =?utf-8?Q?Sch=C3=B6pfer?= , "Berg Philipp \(HAU-EDS\)" , "Weitner Michael \(HAU-EDS\)" , Daniel Thompson , Loic Poulain , stable@vger.kernel.org Subject: Re: [PATCH] mac80211: fix race in ieee80211_register_hw() References: <1586175677-3061-1-git-send-email-sumit.garg@linaro.org> <87ftdgokao.fsf@tynnyri.adurom.net> <1e352e2130e19aec5aa5fc42db397ad50bb4ad05.camel@sipsolutions.net> <87r1x0zsgk.fsf@kamboji.qca.qualcomm.com> <87imiczrwm.fsf@kamboji.qca.qualcomm.com> Date: Mon, 06 Apr 2020 16:27:00 +0300 In-Reply-To: (Sumit Garg's message of "Mon, 6 Apr 2020 18:51:04 +0530") Message-ID: <87v9mcycbf.fsf@kamboji.qca.qualcomm.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Sumit Garg writes: > On Mon, 6 Apr 2020 at 18:38, Johannes Berg wrote: >> >> On Mon, 2020-04-06 at 16:04 +0300, Kalle Valo wrote: >> > Johannes Berg writes: >> > >> > > On Mon, 2020-04-06 at 15:52 +0300, Kalle Valo wrote: >> > > > Johannes Berg writes: >> > > > >> > > > > On Mon, 2020-04-06 at 15:44 +0300, Kalle Valo wrote: >> > > > > > > user-space ieee80211_register_hw() RX IRQ >> > > > > > > +++++++++++++++++++++++++++++++++++++++++++++ >> > > > > > > | | | >> > > > > > > |<---wlan0---wiphy_register() | >> > > > > > > |----start wlan0---->| | >> > > > > > > | |<---IRQ---(RX packet) >> > > > > > > | Kernel crash | >> > > > > > > | due to unallocated | >> > > > > > > | workqueue. | >> > > > > >> > > > > [snip] >> > > > > >> > > > > > I have understood that no frames should be received until mac80211 calls >> > > > > > struct ieee80211_ops::start: >> > > > > > >> > > > > > * @start: Called before the first netdevice attached to the hardware >> > > > > > * is enabled. This should turn on the hardware and must turn on >> > > > > > * frame reception (for possibly enabled monitor interfaces.) >> > > > > >> > > > > True, but I think he's saying that you can actually add and configure an >> > > > > interface as soon as the wiphy is registered? >> > > > >> > > > With '<---IRQ---(RX packet)' I assumed wcn36xx is delivering a frame to >> > > > mac80211 using ieee80211_rx(), but of course I'm just guessing here. >> > > >> > > Yeah, but that could be legitimate? >> > >> > Ah, I misunderstood then. The way I have understood is that no rx frames >> > should be delivered (= calling ieee80211_rx()_ before start() is called, >> > but if that's not the case please ignore me :) >> >> No no, that _is_ the case. But I think the "start wlan0" could end up >> calling it? >> > > Sorry if I wasn't clear enough via the sequence diagram. It's a common > RX packet that arrives via ieee80211_tasklet_handler() which is > enabled via call to "struct ieee80211_ops::start" api. Ah sorry, I didn't realise that. So wcn36xx is not to be blamed then, thanks for the clarification. -- https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches