From patchwork Mon Jun 24 21:01:09 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jason Gunthorpe X-Patchwork-Id: 11014109 X-Patchwork-Delegate: jgg@ziepe.ca Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7EDC0186E for ; Mon, 24 Jun 2019 21:02:08 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 6DDDC288FC for ; Mon, 24 Jun 2019 21:02:08 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 61ACD2891A; Mon, 24 Jun 2019 21:02:08 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0241128949 for ; Mon, 24 Jun 2019 21:02:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728372AbfFXVCH (ORCPT ); Mon, 24 Jun 2019 17:02:07 -0400 Received: from mail-wm1-f67.google.com ([209.85.128.67]:50183 "EHLO mail-wm1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728059AbfFXVCH (ORCPT ); Mon, 24 Jun 2019 17:02:07 -0400 Received: by mail-wm1-f67.google.com with SMTP id c66so688165wmf.0 for ; Mon, 24 Jun 2019 14:02:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=yY5nuWFfvtGdjXx5X0jOTLVoM6UrkzhjnRnf2/dFDmQ=; b=F8IpBc2pCC9TRRcnAQyPopBTGejfFjN4O3manyf4o/rILQiqjMrQn93gZmQT0zfX3x 5Z+FOf3huG56JiHRxImMjpmYUHWLJoUWRxsyiLyvuER8NJ6yXAhiFhmoMeS3xXIFDdo2 S8cp9J0djUNYJQZ5sFZYQ/C2WzaQmeRBmrPgWsubS3c8Ie4OcoFe0BbQ1hX51zSmNWX8 jRx4QvWLtE9d+wLs0Pn2yh3tjD1LsHbOoGDIFKF99fyOS9uFazFhPFuBYcSfa5SLimKH 7oBiYCs7lU7Wqx9ujUyjct2anJPQXnJ7qZm2I66poFSkOkPL9DAIWEUtnwKp1WVc7xDc HnQg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=yY5nuWFfvtGdjXx5X0jOTLVoM6UrkzhjnRnf2/dFDmQ=; b=lqPzpCajTfqUCJIXSOLffUTIIvDfiablaiO35CnrOCEmHr9i3OhDtBNykq6XVLbxWI e00K6Y0OzOafCEpjawGPlLdg7Jf+kaAgTl9DRpbNd3TGkP0+fiKEFu+Fq1oVHNA/dRsX +e0aL2xYflW3II5ebZqZhKlJeC/iPHUxqP7cxroCehAwhmta/pGPgk/Pj3G1whMuUIbh xogR473EOPhmF8P0HXcov1iqrZ5PqpQ92YEghlyQ0DUFeWVbjhWzTDJaYd+tvgPghYNi c/r9fEHCEs177X8geOzZObUdoIAR6QJTlRaGRbMZHnGkwpM+Ob/YZ65w+/4tLlqhPdRY 1OKw== X-Gm-Message-State: APjAAAXvlbH9ihTXfGjGyf3eEkKr6o8MiDdqwlwJEw9V4YC2fA2fPE+a hf6JX5n9Jd7rrlpE7hoPCq7WYQ== X-Google-Smtp-Source: APXvYqyRMuYsh8UNUKwpWttANdd8lJKeiEYwmSXHHDDyx29FbNSbr+pndqxDZmcjLhM+HZNLBH9CVQ== X-Received: by 2002:a1c:4054:: with SMTP id n81mr17413906wma.78.1561410125081; Mon, 24 Jun 2019 14:02:05 -0700 (PDT) Received: from ziepe.ca ([66.187.232.66]) by smtp.gmail.com with ESMTPSA id f7sm6578766wrv.38.2019.06.24.14.02.02 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 24 Jun 2019 14:02:02 -0700 (PDT) Received: from jgg by jggl.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1hfW6D-0001N1-4V; Mon, 24 Jun 2019 18:02:01 -0300 From: Jason Gunthorpe To: Jerome Glisse , Ralph Campbell , John Hubbard , Felix.Kuehling@amd.com Cc: linux-rdma@vger.kernel.org, linux-mm@kvack.org, Andrea Arcangeli , dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, Ben Skeggs , Christoph Hellwig , Philip Yang , Ira Weiny , Jason Gunthorpe Subject: [PATCH v4 hmm 11/12] mm/hmm: Remove confusing comment and logic from hmm_release Date: Mon, 24 Jun 2019 18:01:09 -0300 Message-Id: <20190624210110.5098-12-jgg@ziepe.ca> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190624210110.5098-1-jgg@ziepe.ca> References: <20190624210110.5098-1-jgg@ziepe.ca> MIME-Version: 1.0 Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Jason Gunthorpe hmm_release() is called exactly once per hmm. ops->release() cannot accidentally trigger any action that would recurse back onto hmm->mirrors_sem. This fixes a use after-free race of the form: CPU0 CPU1 hmm_release() up_write(&hmm->mirrors_sem); hmm_mirror_unregister(mirror) down_write(&hmm->mirrors_sem); up_write(&hmm->mirrors_sem); kfree(mirror) mirror->ops->release(mirror) The only user we have today for ops->release is an empty function, so this is unambiguously safe. As a consequence of plugging this race drivers are not allowed to register/unregister mirrors from within a release op. Signed-off-by: Jason Gunthorpe Tested-by: Philip Yang Reviewed-by: Christoph Hellwig --- mm/hmm.c | 28 +++++++++------------------- 1 file changed, 9 insertions(+), 19 deletions(-) diff --git a/mm/hmm.c b/mm/hmm.c index c30aa9403dbe4d..b224ea635a7716 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -130,26 +130,16 @@ static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm) */ WARN_ON(!list_empty_careful(&hmm->ranges)); - down_write(&hmm->mirrors_sem); - mirror = list_first_entry_or_null(&hmm->mirrors, struct hmm_mirror, - list); - while (mirror) { - list_del_init(&mirror->list); - if (mirror->ops->release) { - /* - * Drop mirrors_sem so the release callback can wait - * on any pending work that might itself trigger a - * mmu_notifier callback and thus would deadlock with - * us. - */ - up_write(&hmm->mirrors_sem); + down_read(&hmm->mirrors_sem); + list_for_each_entry(mirror, &hmm->mirrors, list) { + /* + * Note: The driver is not allowed to trigger + * hmm_mirror_unregister() from this thread. + */ + if (mirror->ops->release) mirror->ops->release(mirror); - down_write(&hmm->mirrors_sem); - } - mirror = list_first_entry_or_null(&hmm->mirrors, - struct hmm_mirror, list); } - up_write(&hmm->mirrors_sem); + up_read(&hmm->mirrors_sem); hmm_put(hmm); } @@ -279,7 +269,7 @@ void hmm_mirror_unregister(struct hmm_mirror *mirror) struct hmm *hmm = mirror->hmm; down_write(&hmm->mirrors_sem); - list_del_init(&mirror->list); + list_del(&mirror->list); up_write(&hmm->mirrors_sem); hmm_put(hmm); }