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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C8222C74A5B for ; Tue, 21 Mar 2023 12:06:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231184AbjCUMDQ (ORCPT ); Tue, 21 Mar 2023 08:03:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46268 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229754AbjCUMDP (ORCPT ); Tue, 21 Mar 2023 08:03:15 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 47FAA4BEB1; Tue, 21 Mar 2023 05:03:07 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 01DDAB8163C; Tue, 21 Mar 2023 12:03:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E63E9C433D2; Tue, 21 Mar 2023 12:03:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1679400184; bh=DKgnq/M13pVNuOOzlN17KcsCEqglAFkiJvFXeQc14tY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZTUDQ+Z8AoG9dETJAMaRUyYvcscd8EKkf2P1rQCDGhVhJ2XfPpC+k+xuN5oT87hAS 8krEakNiwmZH1Pw7mdfDPj5pfDrTOU0zmOBIH2z+nPHtmUG8FV7tuZkf6QPPuL6+5S xw/lkQ7PMK9fgFoP0ezlQlaI8ZHU7HALtiCT5kfomuSeKRzgv/H6n7jRgyADaKKSrc 4sjYMSGREOgM2njuAsg75YwOyadqJo4kZ2FcMjnE10kfLF3Q/sR8iLpxGh5Zuk6DR7 QOB+cIAreSjQVe70+k4JXgl9rV0rJI5e1m/M0vf9aY7jkHtJzk8Farp7qg7FnfKKth DVF7SxS8OiZ2g== Date: Tue, 21 Mar 2023 14:02:59 +0200 From: Leon Romanovsky To: Jason Gunthorpe Cc: Patrisious Haddad , "David S. Miller" , Eric Dumazet , Jakub Kicinski , linux-rdma@vger.kernel.org, netdev@vger.kernel.org, Paolo Abeni , Saeed Mahameed Subject: Re: [PATCH rdma-next v1 2/3] RDMA/mlx5: Handling dct common resource destruction upon firmware failure Message-ID: <20230321120259.GT36557@unreal> References: <1a064e9d1b372a73860faf053b3ac12c3315e2cd.1678973858.git.leon@kernel.org> <20230321075458.GP36557@unreal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Mar 21, 2023 at 08:53:35AM -0300, Jason Gunthorpe wrote: > On Tue, Mar 21, 2023 at 09:54:58AM +0200, Leon Romanovsky wrote: > > On Mon, Mar 20, 2023 at 04:18:14PM -0300, Jason Gunthorpe wrote: > > > On Thu, Mar 16, 2023 at 03:39:27PM +0200, Leon Romanovsky wrote: > > > > From: Patrisious Haddad > > > > > > > > Previously when destroying a DCT, if the firmware function for the > > > > destruction failed, the common resource would have been destroyed > > > > either way, since it was destroyed before the firmware object. > > > > Which leads to kernel warning "refcount_t: underflow" which indicates > > > > possible use-after-free. > > > > Which is triggered when we try to destroy the common resource for the > > > > second time and execute refcount_dec_and_test(&common->refcount). > > > > > > > > So, currently before destroying the common resource we check its > > > > refcount and continue with the destruction only if it isn't zero. > > > > > > This seems super sketchy > > > > > > If the destruction fails why not set the refcount back to 1? > > > > Because destruction will fail in destroy_rq_tracked() which is after > > destroy_resource_common(). > > > > In first destruction attempt, we delete qp from radix tree and wait for all > > reference to drop. In order do not undo all this logic (setting 1 alone is > > not enough), it is much safer simply skip destroy_resource_common() in reentry > > case. > > This is the bug I pointed a long time ago, it is ordered wrong to > remove restrack before destruction is assured It is not restrack, but internal to mlx5_core structure. 176 static void destroy_resource_common(struct mlx5_ib_dev *dev, 177 struct mlx5_core_qp *qp) 178 { 179 struct mlx5_qp_table *table = &dev->qp_table; 180 unsigned long flags; 181 .... 185 spin_lock_irqsave(&table->lock, flags); 186 radix_tree_delete(&table->tree, 187 qp->qpn | (qp->common.res << MLX5_USER_INDEX_LEN)); 188 spin_unlock_irqrestore(&table->lock, flags); 189 mlx5_core_put_rsc((struct mlx5_core_rsc_common *)qp); 190 wait_for_completion(&qp->common.free); 191 } > > Jason