From patchwork Tue Mar 6 17:33:12 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tejun Heo X-Patchwork-Id: 10262315 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 1886C602C8 for ; Tue, 6 Mar 2018 17:34:38 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 07DC928AD5 for ; Tue, 6 Mar 2018 17:34:38 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id F02CC28B53; Tue, 6 Mar 2018 17:34:37 +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=-6.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID 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 550E128AD5 for ; Tue, 6 Mar 2018 17:34:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932646AbeCFRef (ORCPT ); Tue, 6 Mar 2018 12:34:35 -0500 Received: from mail-yw0-f195.google.com ([209.85.161.195]:33761 "EHLO mail-yw0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932604AbeCFRee (ORCPT ); Tue, 6 Mar 2018 12:34:34 -0500 Received: by mail-yw0-f195.google.com with SMTP id l200so7216515ywb.0; Tue, 06 Mar 2018 09:34:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references; bh=BizgwUPkxZFcerMykfid3sJPS6OUA8kmmCyGoQUnzYE=; b=Wi+tikhzji0T2y9ab+jT0nKcPaaF8Z+uqmk9YgQ6lBnD2g6SDwcYzeWVv2eAdsOvZY pJaDHibM+K/PpKkPTpOFFS+WU0Xwipqc2dSG4natOR78uCo7ifq5A2Q/+pkWp/X3dRcP /dejhNgH2l7eeMKIDv8NNVKjm2aRjNKLjOuIvppFwTiPYukjtzP0XgV11tj2n9eRyVNQ zwdKkX9AOqoa1bWXNRzpgaWTYBH7olGHi8jd2EmVbPxSjIb3Bbv5lk5KVdqua+mdRmNl eLhU548YZnAS/8bTNE+2nvkvUxrnz5sZPvVXOGWseuzYdphR2fyNnKMHYjhYKl9ec89O 3FVw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:to:cc:subject:date:message-id :in-reply-to:references; bh=BizgwUPkxZFcerMykfid3sJPS6OUA8kmmCyGoQUnzYE=; b=sDWARxBgolWXvbCr/gNxFkee2BHJ6vVo3xbLohp0LHXKsvBnW8Hu11foPmR0RklvTk z6/bZot7nvwjmXxTdWJYP0ZvvK6PIcTHMnmEQA4d5fljpWkz9t5DN4GtlvZwUr8JYddB g05Y9ztJZ/p3aXgIqq/40dHuSU7pdkooa3m/SbqmuNrwzhXTquOKcKADCCZMlVm29LPD cICcz/0VncZeA+H/nk94S0YLOTAD+nCzD9mzFXkg3tbSPDSwBithrTq14VtQyoBFP/YM J2R7jx1iSU59PWtY4R/pJW3hKhhZTSRh0V5sykggbnz3wHuVyO5LuQSJeJ8/pbBWflFj i0Sw== X-Gm-Message-State: APf1xPDyRgimaS2AABhF2vaZYzvlnonT/YSnrOTXwkAebiw54LBiOLcH ssA/HSNUttjnFWCQj1SHvXQ= X-Google-Smtp-Source: AG47ELus1vmMa9Z8oNk1bF/qBLH7JZRSa/w3MUV1P+IvsMzCV0YJ8FRnQ55hwKoVln+Rv46njHb8PA== X-Received: by 10.129.46.2 with SMTP id u2mr12026367ywu.309.1520357674061; Tue, 06 Mar 2018 09:34:34 -0800 (PST) Received: from localhost ([2620:10d:c091:180::1:af9]) by smtp.gmail.com with ESMTPSA id u24sm6156700ywh.15.2018.03.06.09.34.30 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 06 Mar 2018 09:34:33 -0800 (PST) From: Tejun Heo To: torvalds@linux-foundation.org, jannh@google.com, paulmck@linux.vnet.ibm.com, bcrl@kvack.org, viro@zeniv.linux.org.uk, kent.overstreet@gmail.com Cc: security@kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Tejun Heo , Dennis Dalessandro , Mike Marciniszyn , linux-rdma@vger.kernel.org Subject: [PATCH 3/7] RDMAVT: Fix synchronization around percpu_ref Date: Tue, 6 Mar 2018 09:33:12 -0800 Message-Id: <20180306173316.3088458-3-tj@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20180306173316.3088458-1-tj@kernel.org> References: <20180306172657.3060270-1-tj@kernel.org> <20180306173316.3088458-1-tj@kernel.org> 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 rvt_mregion uses percpu_ref for reference counting and RCU to protect accesses from lkey_table. When a rvt_mregion needs to be freed, it first gets unregistered from lkey_table and then rvt_check_refs() is called to wait for in-flight usages before the rvt_mregion is freed. rvt_check_refs() seems to have a couple issues. * It has a fast exit path which tests percpu_ref_is_zero(). However, a percpu_ref reading zero doesn't mean that the object can be released. In fact, the ->release() callback might not even have started executing yet. Proceeding with freeing can lead to use-after-free. * lkey_table is RCU protected but there is no RCU grace period in the free path. percpu_ref uses RCU internally but it's sched-RCU whose grace periods are different from regular RCU. Also, it generally isn't a good idea to depend on internal behaviors like this. To address the above issues, this patch removes the the fast exit and adds an explicit synchronize_rcu(). Signed-off-by: Tejun Heo Cc: Dennis Dalessandro Cc: Mike Marciniszyn Cc: linux-rdma@vger.kernel.org Cc: Linus Torvalds Acked-by: Dennis Dalessandro --- Hello, Dennis, Mike. I don't know RDMA at all and this patch is only compile tested. Can you please take a careful look? Thanks. drivers/infiniband/sw/rdmavt/mr.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/drivers/infiniband/sw/rdmavt/mr.c b/drivers/infiniband/sw/rdmavt/mr.c index 1b2e536..cc429b5 100644 --- a/drivers/infiniband/sw/rdmavt/mr.c +++ b/drivers/infiniband/sw/rdmavt/mr.c @@ -489,11 +489,13 @@ static int rvt_check_refs(struct rvt_mregion *mr, const char *t) unsigned long timeout; struct rvt_dev_info *rdi = ib_to_rvt(mr->pd->device); - if (percpu_ref_is_zero(&mr->refcount)) - return 0; - /* avoid dma mr */ - if (mr->lkey) + if (mr->lkey) { + /* avoid dma mr */ rvt_dereg_clean_qps(mr); + /* @mr was indexed on rcu protected @lkey_table */ + synchronize_rcu(); + } + timeout = wait_for_completion_timeout(&mr->comp, 5 * HZ); if (!timeout) { rvt_pr_err(rdi,