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[23.128.96.18]) by mx.google.com with ESMTP id q10si8237925eja.345.2020.05.24.08.35.53; Sun, 24 May 2020 08:36:17 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@web.de header.s=dbaedf251592 header.b=eNTRFVPA; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729338AbgEXPdO (ORCPT + 99 others); Sun, 24 May 2020 11:33:14 -0400 Received: from mout.web.de ([212.227.15.3]:57735 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727027AbgEXPdN (ORCPT ); Sun, 24 May 2020 11:33:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=web.de; s=dbaedf251592; t=1590334384; bh=RvgPa4HlNKsPOWlekAAfTVT3667QgjoEs86JI0r2Qeg=; h=X-UI-Sender-Class:To:Cc:Subject:From:Date; b=eNTRFVPAcfD0k8Jgb5em/LgdMeU+YlNZ8Qgd8JbhW2S2pFuv3bvTPH+VpX/iQSzpz 1cCt9LsQTPro0tmPVPaJeMRQvI/oLNinUDe+NOWXbemvg2T/nKKAVfybJaR2Wh1Okz AZvUQh5FMcRuQ1JS8bU8uh00aM1ceH//hQh2OVyc= X-UI-Sender-Class: c548c8c5-30a9-4db5-a2e7-cb6cb037b8f9 Received: from [192.168.1.2] ([93.132.187.46]) by smtp.web.de (mrweb006 [213.165.67.108]) with ESMTPSA (Nemesis) id 1N45xt-1iv7cc3Phh-0101UC; Sun, 24 May 2020 17:33:03 +0200 To: Zhang Qiang , Lai Jiangshan , Tejun Heo Cc: linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org Subject: Re: [PATCH] workqueue: Fix double kfree(rescuer) in destroy_workqueue() From: Markus Elfring Autocrypt: addr=Markus.Elfring@web.de; prefer-encrypt=mutual; keydata= mQINBFg2+xABEADBJW2hoUoFXVFWTeKbqqif8VjszdMkriilx90WB5c0ddWQX14h6w5bT/A8 +v43YoGpDNyhgA0w9CEhuwfZrE91GocMtjLO67TAc2i2nxMc/FJRDI0OemO4VJ9RwID6ltwt mpVJgXGKkNJ1ey+QOXouzlErVvE2fRh+KXXN1Q7fSmTJlAW9XJYHS3BDHb0uRpymRSX3O+E2 lA87C7R8qAigPDZi6Z7UmwIA83ZMKXQ5stA0lhPyYgQcM7fh7V4ZYhnR0I5/qkUoxKpqaYLp YHBczVP+Zx/zHOM0KQphOMbU7X3c1pmMruoe6ti9uZzqZSLsF+NKXFEPBS665tQr66HJvZvY GMDlntZFAZ6xQvCC1r3MGoxEC1tuEa24vPCC9RZ9wk2sY5Csbva0WwYv3WKRZZBv8eIhGMxs rcpeGShRFyZ/0BYO53wZAPV1pEhGLLxd8eLN/nEWjJE0ejakPC1H/mt5F+yQBJAzz9JzbToU 5jKLu0SugNI18MspJut8AiA1M44CIWrNHXvWsQ+nnBKHDHHYZu7MoXlOmB32ndsfPthR3GSv jN7YD4Ad724H8fhRijmC1+RpuSce7w2JLj5cYj4MlccmNb8YUxsE8brY2WkXQYS8Ivse39MX BE66MQN0r5DQ6oqgoJ4gHIVBUv/ZwgcmUNS5gQkNCFA0dWXznQARAQABtCZNYXJrdXMgRWxm cmluZyA8TWFya3VzLkVsZnJpbmdAd2ViLmRlPokCVAQTAQgAPhYhBHDP0hzibeXjwQ/ITuU9 Figxg9azBQJYNvsQAhsjBQkJZgGABQsJCAcCBhUICQoLAgQWAgMBAh4BAheAAAoJEOU9Figx g9azcyMP/iVihZkZ4VyH3/wlV3nRiXvSreqg+pGPI3c8J6DjP9zvz7QHN35zWM++1yNek7Ar OVXwuKBo18ASlYzZPTFJZwQQdkZSV+atwIzG3US50ZZ4p7VyUuDuQQVVqFlaf6qZOkwHSnk+ CeGxlDz1POSHY17VbJG2CzPuqMfgBtqIU1dODFLpFq4oIAwEOG6fxRa59qbsTLXxyw+PzRaR LIjVOit28raM83Efk07JKow8URb4u1n7k9RGAcnsM5/WMLRbDYjWTx0lJ2WO9zYwPgRykhn2 sOyJVXk9xVESGTwEPbTtfHM+4x0n0gC6GzfTMvwvZ9G6xoM0S4/+lgbaaa9t5tT/PrsvJiob kfqDrPbmSwr2G5mHnSM9M7B+w8odjmQFOwAjfcxoVIHxC4Cl/GAAKsX3KNKTspCHR0Yag78w i8duH/eEd4tB8twcqCi3aCgWoIrhjNS0myusmuA89kAWFFW5z26qNCOefovCx8drdMXQfMYv g5lRk821ZCNBosfRUvcMXoY6lTwHLIDrEfkJQtjxfdTlWQdwr0mM5ye7vd83AManSQwutgpI q+wE8CNY2VN9xAlE7OhcmWXlnAw3MJLW863SXdGlnkA3N+U4BoKQSIToGuXARQ14IMNvfeKX NphLPpUUnUNdfxAHu/S3tPTc/E/oePbHo794dnEm57LuuQINBFg2+xABEADZg/T+4o5qj4cw nd0G5pFy7ACxk28mSrLuva9tyzqPgRZ2bdPiwNXJUvBg1es2u81urekeUvGvnERB/TKekp25 4wU3I2lEhIXj5NVdLc6eU5czZQs4YEZbu1U5iqhhZmKhlLrhLlZv2whLOXRlLwi4jAzXIZAu 76mT813jbczl2dwxFxcT8XRzk9+dwzNTdOg75683uinMgskiiul+dzd6sumdOhRZR7YBT+xC wzfykOgBKnzfFscMwKR0iuHNB+VdEnZw80XGZi4N1ku81DHxmo2HG3icg7CwO1ih2jx8ik0r riIyMhJrTXgR1hF6kQnX7p2mXe6K0s8tQFK0ZZmYpZuGYYsV05OvU8yqrRVL/GYvy4Xgplm3 DuMuC7/A9/BfmxZVEPAS1gW6QQ8vSO4zf60zREKoSNYeiv+tURM2KOEj8tCMZN3k3sNASfoG fMvTvOjT0yzMbJsI1jwLwy5uA2JVdSLoWzBD8awZ2X/eCU9YDZeGuWmxzIHvkuMj8FfX8cK/ 2m437UA877eqmcgiEy/3B7XeHUipOL83gjfq4ETzVmxVswkVvZvR6j2blQVr+MhCZPq83Ota xNB7QptPxJuNRZ49gtT6uQkyGI+2daXqkj/Mot5tKxNKtM1Vbr/3b+AEMA7qLz7QjhgGJcie qp4b0gELjY1Oe9dBAXMiDwARAQABiQI8BBgBCAAmFiEEcM/SHOJt5ePBD8hO5T0WKDGD1rMF Alg2+xACGwwFCQlmAYAACgkQ5T0WKDGD1rOYSw/+P6fYSZjTJDAl9XNfXRjRRyJSfaw6N1pA Ahuu0MIa3djFRuFCrAHUaaFZf5V2iW5xhGnrhDwE1Ksf7tlstSne/G0a+Ef7vhUyeTn6U/0m +/BrsCsBUXhqeNuraGUtaleatQijXfuemUwgB+mE3B0SobE601XLo6MYIhPh8MG32MKO5kOY hB5jzyor7WoN3ETVNQoGgMzPVWIRElwpcXr+yGoTLAOpG7nkAUBBj9n9TPpSdt/npfok9ZfL /Q+ranrxb2Cy4tvOPxeVfR58XveX85ICrW9VHPVq9sJf/a24bMm6+qEg1V/G7u/AM3fM8U2m tdrTqOrfxklZ7beppGKzC1/WLrcr072vrdiN0icyOHQlfWmaPv0pUnW3AwtiMYngT96BevfA qlwaymjPTvH+cTXScnbydfOQW8220JQwykUe+sHRZfAF5TS2YCkQvsyf7vIpSqo/ttDk4+xc Z/wsLiWTgKlih2QYULvW61XU+mWsK8+ZlYUrRMpkauN4CJ5yTpvp+Orcz5KixHQmc5tbkLWf x0n1QFc1xxJhbzN+r9djSGGN/5IBDfUqSANC8cWzHpWaHmSuU3JSAMB/N+yQjIad2ztTckZY pwT6oxng29LzZspTYUEzMz3wK2jQHw+U66qBFk8whA7B2uAU1QdGyPgahLYSOa4XAEGb6wbI FEE= Message-ID: <96b49f22-50a7-9c8f-7c9d-f178195de717@web.de> Date: Sun, 24 May 2020 17:33:02 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:mOD4CB+9dD1DHW4Qao41dV9PM62AVLbj+yo4k9fbpMtKkcvfpEk DVg3ALUHUigWgIp/rjL6mv7gF/b+r3j/YBENYb6uF9GlRmqaD5pGEI6cN5aYpXO8JZFTvB2 jaR2SAQjjW0wdBsiD+TSD9ShZsFKj4RTRwHOQVlwIBh9O5ZyzqSlqbdfnp1VUj6hgjTWplh gqsmI0JYFW2Ob3Ls1fS+Q== X-Spam-Flag: NO X-UI-Out-Filterresults: notjunk:1;V03:K0:peOpKegWxJI=:U28k7U/C75VtPYdRc2nV37 w926RpLs7NjWfbkEz9+n5osTFLWAPTB5SfCIZ/lS3YOCyGeG9/BCevDlM8HdfqVDhH5zufOfP ijI8lI3qZqmcnt/ITwL2kQIyrRyxE7rcF0uF1+i2gL/8/fcHyooaey4HyNeLMFvFP642zvMkm 15+oNVq7snnxLUF7MYbC02bIDbMp3Ox56SQFYNzWr5DpPYu8JhIK18Yc0y7BvVbywgSVnTdJU WDwwotyOkJ3Dkqwc01V28PVLk6hdkTClGF9QWe0oBDjIR/3yk8GZKvaLhiAxfE3TXSEI7cNs2 lXNoqsinenrQa5nzrKFnzJPeN3BRvLfCinVJ0kKFsh4tNDpoAAe8deAuTv5LfbJJoo4ZLlR5z WFzKmTFMGsMCjmfKYCVo32L5jMInnc7/85856id8rZB6YkiD2WIk3nzIG/f71AU94o3NVoTvS mRTfxx0PICE5kCRjVCp4I4xH5eTJohH9NCw9vm/RaUtj4AbyVCGDPcTZfdWpZTdNPEfbWeZAX 5yWKQYOzlBENL1Fr5sHDu+wnmpq7uIW5gJNfCTp5IRk3Y3Kr7WSUSrL4Kld+nf9ZUkFralGI7 RFn8bv2oWxGqnCiJU2dPKx3LArCkVTO7aZcwQPGkO7Ww/EjZrE6zxQMaT4QmLduv8Ynm7/rY3 8EKXWW4Mui9rr5RI11XPG94kkgRv+opEPbMav0toTp3rW2lXakewbwK4c/mlCF7Gl5jfIKwjh AFtMImG53eO278ojqYSsNr6puvBzR+AzHd7s5LlVXVi6hWDj8gUBBsu2EMQWIRNEoEOseZ2zW jHdCe7ocVL+g8W8w10kuCTr6fUZ9XGKgqMZwmS9l9iJ7xRuJnF7bm0HmYuBSO+yIFPhVW+d3l TzTL4/2xMcBsZ86gq8JUSeDdP3BDUaVZvNNmw0HRSSi6lDBA6p+7W7CyeTF9JvpwT0xot/yxQ YVoweT4wXyY8vntujWYCXsa99eY8EQOPcJsnVdU42+XSpM/yCyJCkGqHRB/6VPI3wLkgX5p5I JLWwlH5FQcZeFTxSKvURgXBhZ3plcYIVqMo0mkBnsRnLclTbFyGY+p6Hp9XqOD5sqcS3GeSTN hV2zTW+vmboeZdPHhIBrkttQwpoKJnd/8syxi8AUZLrv9hf57g1y/OeCWuwSEl8W3u3auaAC/ yhyAqk344nrqJB5oxWNWVySIMEebFIBtHa3Gd61CBCKXBOLNFGxWBIIFQ/V1jS/aX/U4tdFDZ X/RVmd9KwcQXK6b4n Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > When destroy_workqueue if rescuer worker exist,wq->rescuer pointer be > kfree. if sanity checks passed. the func call_rcu(&wq->rcu, rcu_free_wq) > will be called if the wq->flags & WQ_UNBOUND is false,in rcu_free_wq > func wq->rescuer pointer was kfree again. 1. I suggest to improve also this change description. Do you try to explain here that a call of the function =E2=80=9Cfree_wo= rkqueue_attrs=E2=80=9D (or =E2=80=9Cfree_percpu=E2=80=9D) would perform sufficient clean-up of= system resources in this use case? 2. You proposed to delete the function call =E2=80=9Ckfree(wq->rescuer)=E2= =80=9D from the implementation of the function =E2=80=9Crcu_free_wq=E2=80=9D. https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tre= e/kernel/workqueue.c?id=3Dc11d28ab4a691736e30b49813fb801847bd44e83#n3482 https://elixir.bootlin.com/linux/v5.7-rc6/source/kernel/workqueue.c#L34= 82 This function name should be specified also in the patch subject, shouldn't it? 3. Would you like to add the tag =E2=80=9CFixes=E2=80=9D to the commit mes= sage? Regards, Markus