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=-18.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 1634DC432BE for ; Tue, 10 Aug 2021 23:25:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E799660240 for ; Tue, 10 Aug 2021 23:25:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235432AbhHJX0R (ORCPT ); Tue, 10 Aug 2021 19:26:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47280 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235372AbhHJX0P (ORCPT ); Tue, 10 Aug 2021 19:26:15 -0400 Received: from mail-il1-x12e.google.com (mail-il1-x12e.google.com [IPv6:2607:f8b0:4864:20::12e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 45914C0613D3 for ; Tue, 10 Aug 2021 16:25:53 -0700 (PDT) Received: by mail-il1-x12e.google.com with SMTP id z2so913712iln.0 for ; Tue, 10 Aug 2021 16:25:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=bZoaI6O41jzGVQVv3zA5uioisseRRe2gwUb7pdILMzk=; b=J1THLu5eYNZtHM3lMmUt7+OIXk7EVRLducZPFSwhsbu7Wk4lhibTkc9mfy14DXZFVm Ij2B/6k1OdBopiZyqYG5AyQ3vpBHY+5UJvl7PeYTVWvlnJcwN6+I8gSkQSIt0FrKdHOT JY0IbEXZ4pbRdu+WUknNYe11HdUNbaAjxFMyw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=bZoaI6O41jzGVQVv3zA5uioisseRRe2gwUb7pdILMzk=; b=YenC4loyMhueQy9ChTITdKT132mK7bViK/BrIVPfJwC6vj72YhCrTs+i2c3Dsq0dke rgnNTWqzfJmpCG2KUl7ajUr9w1z0kXb5L+itApomcPmPPrqHYrNI4leJ/FfhIYVan8oS kVbP89JReJRs/Fauq1+r/9BBJEe3cgbVeQGAB3wzdqMl6Lvo2hjMS5FhnQQ+IqOw4Rm5 4WFXWI5p44raM/9j0NVQl1scdXLk0hg3+IovHYtGK5r4CM5azDF5GPIau7Ms5BRUiVWT Oxgm9QcJ0J89YoL1kNEf3WBH9aOUr2rsO0dW07y23e6h3Cm0KqB6Ex735cUGi3ulmTZN YiXA== X-Gm-Message-State: AOAM531AbYM1op+xm0lhjEUG83XCc9RKwQ9xx8m6fnzKK4gTtEIjfcfq FceGN8GEt/Dmj+IMJ7TT/ds5ig== X-Google-Smtp-Source: ABdhPJxMNwaUBHMUh5ydhrrgGMfKNzKN3s40bG9zf8K8L6avCCj/BcE/ZK9vDoaT7kTDUxa28SRgsg== X-Received: by 2002:a92:bf03:: with SMTP id z3mr361512ilh.196.1628637952654; Tue, 10 Aug 2021 16:25:52 -0700 (PDT) Received: from [192.168.1.112] (c-24-9-64-241.hsd1.co.comcast.net. [24.9.64.241]) by smtp.gmail.com with ESMTPSA id v5sm12552039ilu.19.2021.08.10.16.25.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Aug 2021 16:25:52 -0700 (PDT) Subject: Re: [PATCH v2] usbip: give back URBs for unsent unlink requests during cleanup To: Anirudh Rayabharam , Valentina Manea , Shuah Khan , Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, linux-usb@vger.kernel.org, syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com, Shuah Khan References: <20210806181335.2078-1-mail@anirudhrb.com> From: Shuah Khan Message-ID: <4aaf420d-e85e-212e-3bc4-a70e016de610@linuxfoundation.org> Date: Tue, 10 Aug 2021 17:25:51 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210806181335.2078-1-mail@anirudhrb.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/6/21 12:13 PM, Anirudh Rayabharam wrote: > In vhci_device_unlink_cleanup(), the URBs for unsent unlink requests are > not given back. This sometimes causes usb_kill_urb to wait indefinitely > for that urb to be given back. syzbot has reported a hung task issue [1] > for this. > > To fix this, give back the urbs corresponding to unsent unlink requests > (unlink_tx list) similar to how urbs corresponding to unanswered unlink > requests (unlink_rx list) are given back. Since the code is almost the > same, extract it into a new function and call it for both unlink_rx and > unlink_tx lists. > Let's not do the refactor - let's first fix the problem and then the refactor. > [1]: https://syzkaller.appspot.com/bug?id=08f12df95ae7da69814e64eb5515d5a85ed06b76 > > Reported-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com > Tested-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com > Signed-off-by: Anirudh Rayabharam > --- > > Changes in v2: > Use WARN_ON() instead of BUG() when unlink_list is neither unlink_tx nor > unlink_rx. > > v1: https://lore.kernel.org/lkml/20210806164015.25263-1-mail@anirudhrb.com/ > > --- > drivers/usb/usbip/vhci_hcd.c | 45 +++++++++++++++++++++++++----------- > 1 file changed, 32 insertions(+), 13 deletions(-) > > diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c > index 4ba6bcdaa8e9..67e638f4c455 100644 > --- a/drivers/usb/usbip/vhci_hcd.c > +++ b/drivers/usb/usbip/vhci_hcd.c > @@ -945,7 +945,8 @@ static int vhci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status) > return 0; > } > > -static void vhci_device_unlink_cleanup(struct vhci_device *vdev) > +static void __vhci_cleanup_unlink_list(struct vhci_device *vdev, > + struct list_head *unlink_list) > { > struct vhci_hcd *vhci_hcd = vdev_to_vhci_hcd(vdev); > struct usb_hcd *hcd = vhci_hcd_to_hcd(vhci_hcd); > @@ -953,23 +954,23 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev) > struct vhci_unlink *unlink, *tmp; > unsigned long flags; > > + if (WARN(unlink_list != &vdev->unlink_tx > + && unlink_list != &vdev->unlink_rx, > + "Invalid list passed to __vhci_cleanup_unlink_list\n")) > + return; > + With this change, this will be only place unlink_rx is used without vdev->priv_lock hold? Please explain why this is safe. > spin_lock_irqsave(&vhci->lock, flags); > spin_lock(&vdev->priv_lock); > > - list_for_each_entry_safe(unlink, tmp, &vdev->unlink_tx, list) { > - pr_info("unlink cleanup tx %lu\n", unlink->unlink_seqnum); > - list_del(&unlink->list); > - kfree(unlink); > - } > - > - while (!list_empty(&vdev->unlink_rx)) { > + list_for_each_entry_safe(unlink, tmp, unlink_list, list) { > struct urb *urb; > > - unlink = list_first_entry(&vdev->unlink_rx, struct vhci_unlink, > - list); > - > - /* give back URB of unanswered unlink request */ > - pr_info("unlink cleanup rx %lu\n", unlink->unlink_seqnum); > + if (unlink_list == &vdev->unlink_tx) > + pr_info("unlink cleanup tx %lu\n", > + unlink->unlink_seqnum); > + else > + pr_info("unlink cleanup rx %lu\n", > + unlink->unlink_seqnum); > > urb = pickup_urb_and_free_priv(vdev, unlink->unlink_seqnum); > if (!urb) { > @@ -1001,6 +1002,24 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev) > spin_unlock_irqrestore(&vhci->lock, flags); > } > > +static inline void vhci_cleanup_unlink_tx(struct vhci_device *vdev) > +{ > + __vhci_cleanup_unlink_list(vdev, &vdev->unlink_tx); With this change, this will be only place unlink_rx is used without vdev->priv_lock hold? Please explain why this is safe. > +} > + Is there a need for this layer? > +static inline void vhci_cleanup_unlink_rx(struct vhci_device *vdev) > +{ > + __vhci_cleanup_unlink_list(vdev, &vdev->unlink_rx); With this change, this will be only place unlink_rx is used without vdev->priv_lock hold? Please explain why this is safe. > +} > + Is there a need for this layer? > +static void vhci_device_unlink_cleanup(struct vhci_device *vdev) > +{ > + /* give back URBs of unsent unlink requests */ > + vhci_cleanup_unlink_tx(vdev); > + /* give back URBs of unanswered unlink requests */ > + vhci_cleanup_unlink_rx(vdev); > +} > + > /* > * The important thing is that only one context begins cleanup. > * This is why error handling and cleanup become simple. > thanks, -- Shuah 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=-15.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 9B1C6C4338F for ; Tue, 10 Aug 2021 23:26:04 +0000 (UTC) Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3B4B16052B for ; Tue, 10 Aug 2021 23:26:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 3B4B16052B Authentication-Results: mail.kernel.org; dmarc=pass (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.linuxfoundation.org Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id F15E5401CA; Tue, 10 Aug 2021 23:26:03 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id so1tjsl66ylr; Tue, 10 Aug 2021 23:26:00 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp2.osuosl.org (Postfix) with ESMTPS id 1E8D2400D0; Tue, 10 Aug 2021 23:26:00 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id E8FB3C001A; Tue, 10 Aug 2021 23:25:59 +0000 (UTC) Received: from smtp2.osuosl.org (smtp2.osuosl.org [IPv6:2605:bc80:3010::133]) by lists.linuxfoundation.org (Postfix) with ESMTP id 648E1C000E for ; Tue, 10 Aug 2021 23:25:58 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 4994F400D0 for ; Tue, 10 Aug 2021 23:25:58 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id zcIm7r_Y0Vuo for ; Tue, 10 Aug 2021 23:25:53 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.8.0 Received: from mail-il1-x12f.google.com (mail-il1-x12f.google.com [IPv6:2607:f8b0:4864:20::12f]) by smtp2.osuosl.org (Postfix) with ESMTPS id A360940012 for ; Tue, 10 Aug 2021 23:25:53 +0000 (UTC) Received: by mail-il1-x12f.google.com with SMTP id i9so832606ilk.9 for ; Tue, 10 Aug 2021 16:25:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=bZoaI6O41jzGVQVv3zA5uioisseRRe2gwUb7pdILMzk=; b=J1THLu5eYNZtHM3lMmUt7+OIXk7EVRLducZPFSwhsbu7Wk4lhibTkc9mfy14DXZFVm Ij2B/6k1OdBopiZyqYG5AyQ3vpBHY+5UJvl7PeYTVWvlnJcwN6+I8gSkQSIt0FrKdHOT JY0IbEXZ4pbRdu+WUknNYe11HdUNbaAjxFMyw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=bZoaI6O41jzGVQVv3zA5uioisseRRe2gwUb7pdILMzk=; b=jiWOxLm6T7q3PeaIrqUVBVMH7Fp5Ot673AnTjfaVUvxjaS2nt91sHXmpAXyEbovyTx MtJIK6eISXUjsepjIMSSU5AGOy1qo0WTcCgRaCd23j0MRelLYEwhqXmp46Sgsrf2D0ZH B3SOCujORl6rMjkvqzPUtAg9hOYDm1QGtdl8puRKrzLcR1rYbbMXHwMA5xlcDfLsvnLd TXp5cfGbMG6Q/YOkMw2p4Fm/WfUWEeEoAgw0JJ5GIFuJ6njqyrMOrKeqtObhY6+uc0pS Rx0l7l9t+oF/wlWXxkrCF8SJGDKfIS91M6tkCKWzaS8kiojQWQWKGBEKqNPYn1ssVwYj KLNA== X-Gm-Message-State: AOAM531u205BzW1UmfJuOfZJd14cnBVJMx/93UerG0eaJK9xDYznw2LL oQiGhRN5Y1dc2uc0ITR9t53tm7CB X-Google-Smtp-Source: ABdhPJxMNwaUBHMUh5ydhrrgGMfKNzKN3s40bG9zf8K8L6avCCj/BcE/ZK9vDoaT7kTDUxa28SRgsg== X-Received: by 2002:a92:bf03:: with SMTP id z3mr361512ilh.196.1628637952654; Tue, 10 Aug 2021 16:25:52 -0700 (PDT) Received: from [192.168.1.112] (c-24-9-64-241.hsd1.co.comcast.net. [24.9.64.241]) by smtp.gmail.com with ESMTPSA id v5sm12552039ilu.19.2021.08.10.16.25.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Aug 2021 16:25:52 -0700 (PDT) Subject: Re: [PATCH v2] usbip: give back URBs for unsent unlink requests during cleanup To: Anirudh Rayabharam , Valentina Manea , Shuah Khan , Greg Kroah-Hartman References: <20210806181335.2078-1-mail@anirudhrb.com> From: Shuah Khan Message-ID: <4aaf420d-e85e-212e-3bc4-a70e016de610@linuxfoundation.org> Date: Tue, 10 Aug 2021 17:25:51 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210806181335.2078-1-mail@anirudhrb.com> Content-Language: en-US Cc: linux-usb@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, linux-kernel@vger.kernel.org, syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com X-BeenThere: linux-kernel-mentees@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: linux-kernel-mentees-bounces@lists.linuxfoundation.org Sender: "Linux-kernel-mentees" On 8/6/21 12:13 PM, Anirudh Rayabharam wrote: > In vhci_device_unlink_cleanup(), the URBs for unsent unlink requests are > not given back. This sometimes causes usb_kill_urb to wait indefinitely > for that urb to be given back. syzbot has reported a hung task issue [1] > for this. > > To fix this, give back the urbs corresponding to unsent unlink requests > (unlink_tx list) similar to how urbs corresponding to unanswered unlink > requests (unlink_rx list) are given back. Since the code is almost the > same, extract it into a new function and call it for both unlink_rx and > unlink_tx lists. > Let's not do the refactor - let's first fix the problem and then the refactor. > [1]: https://syzkaller.appspot.com/bug?id=08f12df95ae7da69814e64eb5515d5a85ed06b76 > > Reported-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com > Tested-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com > Signed-off-by: Anirudh Rayabharam > --- > > Changes in v2: > Use WARN_ON() instead of BUG() when unlink_list is neither unlink_tx nor > unlink_rx. > > v1: https://lore.kernel.org/lkml/20210806164015.25263-1-mail@anirudhrb.com/ > > --- > drivers/usb/usbip/vhci_hcd.c | 45 +++++++++++++++++++++++++----------- > 1 file changed, 32 insertions(+), 13 deletions(-) > > diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c > index 4ba6bcdaa8e9..67e638f4c455 100644 > --- a/drivers/usb/usbip/vhci_hcd.c > +++ b/drivers/usb/usbip/vhci_hcd.c > @@ -945,7 +945,8 @@ static int vhci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status) > return 0; > } > > -static void vhci_device_unlink_cleanup(struct vhci_device *vdev) > +static void __vhci_cleanup_unlink_list(struct vhci_device *vdev, > + struct list_head *unlink_list) > { > struct vhci_hcd *vhci_hcd = vdev_to_vhci_hcd(vdev); > struct usb_hcd *hcd = vhci_hcd_to_hcd(vhci_hcd); > @@ -953,23 +954,23 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev) > struct vhci_unlink *unlink, *tmp; > unsigned long flags; > > + if (WARN(unlink_list != &vdev->unlink_tx > + && unlink_list != &vdev->unlink_rx, > + "Invalid list passed to __vhci_cleanup_unlink_list\n")) > + return; > + With this change, this will be only place unlink_rx is used without vdev->priv_lock hold? Please explain why this is safe. > spin_lock_irqsave(&vhci->lock, flags); > spin_lock(&vdev->priv_lock); > > - list_for_each_entry_safe(unlink, tmp, &vdev->unlink_tx, list) { > - pr_info("unlink cleanup tx %lu\n", unlink->unlink_seqnum); > - list_del(&unlink->list); > - kfree(unlink); > - } > - > - while (!list_empty(&vdev->unlink_rx)) { > + list_for_each_entry_safe(unlink, tmp, unlink_list, list) { > struct urb *urb; > > - unlink = list_first_entry(&vdev->unlink_rx, struct vhci_unlink, > - list); > - > - /* give back URB of unanswered unlink request */ > - pr_info("unlink cleanup rx %lu\n", unlink->unlink_seqnum); > + if (unlink_list == &vdev->unlink_tx) > + pr_info("unlink cleanup tx %lu\n", > + unlink->unlink_seqnum); > + else > + pr_info("unlink cleanup rx %lu\n", > + unlink->unlink_seqnum); > > urb = pickup_urb_and_free_priv(vdev, unlink->unlink_seqnum); > if (!urb) { > @@ -1001,6 +1002,24 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev) > spin_unlock_irqrestore(&vhci->lock, flags); > } > > +static inline void vhci_cleanup_unlink_tx(struct vhci_device *vdev) > +{ > + __vhci_cleanup_unlink_list(vdev, &vdev->unlink_tx); With this change, this will be only place unlink_rx is used without vdev->priv_lock hold? Please explain why this is safe. > +} > + Is there a need for this layer? > +static inline void vhci_cleanup_unlink_rx(struct vhci_device *vdev) > +{ > + __vhci_cleanup_unlink_list(vdev, &vdev->unlink_rx); With this change, this will be only place unlink_rx is used without vdev->priv_lock hold? Please explain why this is safe. > +} > + Is there a need for this layer? > +static void vhci_device_unlink_cleanup(struct vhci_device *vdev) > +{ > + /* give back URBs of unsent unlink requests */ > + vhci_cleanup_unlink_tx(vdev); > + /* give back URBs of unanswered unlink requests */ > + vhci_cleanup_unlink_rx(vdev); > +} > + > /* > * The important thing is that only one context begins cleanup. > * This is why error handling and cleanup become simple. > thanks, -- Shuah _______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees