From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 07CD93AC16; Thu, 6 Jun 2024 07:38:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717659487; cv=none; b=b00IJgNcT63eT35kWN4hZkexjTu9ImKrsN3DAPHPJKiQ+q6D7Qb9agUyDoM3kUqR67fV44c/SfVsDoV6A5bMiTeGhjBKSSYtL993MzvD0P9CQ3SpG85m8rJIQtvGy3MoRFQmPPPF0mrU6v1fsL45P86f1Xf5Fch7qlbuovII8wU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717659487; c=relaxed/simple; bh=BjRy2bONDnwpsYh5J5sDM+y5cxV/N4RQdfo+TuyNLsA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=VPsf3EhWiwx8AZX3pyatJ+9mjNN+UxoTvyDR36ZRe/oL+7CbjftrshOq3tPoszdJToZsBYlJePI0D3frxJE3zh9cnT3M0qzAtUbvbzUxpEVFb8V0iGYvSyDR2TgGtg/Rax525yAqCZOvf/0PeT9Vro1RdFz1+iBQTnHyqi60sHo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hDDoI2mm; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hDDoI2mm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1607BC4AF12; Thu, 6 Jun 2024 07:38:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1717659486; bh=BjRy2bONDnwpsYh5J5sDM+y5cxV/N4RQdfo+TuyNLsA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=hDDoI2mm06p/NCVDMo41ApIhrMhZ2MQL2aIZG3NVsqLoRbI68S2PR1qR8xX5jXnXl F66QPwka8MSRV/7VVK95YTMKgCdznjxm+snZrvQW5T3gRW1NqhXW/XKCa7qM+VK9VV ufh5QEwOTEm4zKrV+0/yAy6SXeOdx8ZqMBsv9T8LA3QLWIH9xWash0LCfJG4B/ADku iA3Yl0gJj6MMMMg7J8j9jM1etcIDjEQ/YSFlPH8Nitgov+hSfG5LSd/vKPZqu/ePw8 ajhy5OyhWJd5E9M3U0jkLPxHMI0MQ/nF2FtOrxE/Suv4F6K1gGDKucvuiLesMwMEGU C5xKoonVhFVfA== Date: Thu, 6 Jun 2024 10:38:01 +0300 From: Leon Romanovsky To: Hillf Danton Cc: Tejun Heo , Peter Zijlstra , Lai Jiangshan , Zqiang , linux-kernel@vger.kernel.org, Gal Pressman , Tariq Toukan , RDMA mailing list Subject: Re: [PATCH -rc] workqueue: Reimplement UAF fix to avoid lockdep worning Message-ID: <20240606073801.GA13732@unreal> References: <4c4f1fb769a609a61010cb6d884ab2841ef716d3.1716885172.git.leon@kernel.org> <20240531034851.GF3884@unreal> <20240604105456.1668-1-hdanton@sina.com> <20240604113834.GO3884@unreal> <20240605111055.1843-1-hdanton@sina.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240605111055.1843-1-hdanton@sina.com> On Wed, Jun 05, 2024 at 07:10:55PM +0800, Hillf Danton wrote: > On Tue, 4 Jun 2024 21:58:04 +0300 Leon Romanovsky > > On Tue, Jun 04, 2024 at 06:30:49AM -1000, Tejun Heo wrote: > > > On Tue, Jun 04, 2024 at 02:38:34PM +0300, Leon Romanovsky wrote: > > > > Thanks, it is very rare situation where call to flush/drain queue > > > > (in our case kthread_flush_worker) in the middle of the allocation > > > > flow can be correct. I can't remember any such case. > > > > > > > > So even we don't fully understand the root cause, the reimplementation > > > > is still valid and improves existing code. > > > > > > It's not valid. pwq release is async and while wq free in the error path > > > isn't. The flush is there so that we finish the async part before > > > synchronize error handling. The patch you posted will can lead to double > > > free after a pwq allocation failure. We can make the error path synchronous > > > but the pwq free path should be updated first so that it stays synchronous > > > in the error path. Note that it *needs* to be asynchronous in non-error > > > paths, so it's going to be a bit subtle one way or the other. > > > > But at that point, we didn't add newly created WQ to any list which will execute > > that asynchronous release. Did I miss something? > > > Maybe it is more subtle than thought, but not difficult to make the wq > allocation path sync. See if the patch could survive your test. Thanks, I started to run our tests with Dan's revert. https://lore.kernel.org/all/171711745834.1628941.5259278474013108507.stgit@dwillia2-xfh.jf.intel.com/ As premature results, it fixed my lockdep warnings, but it will take time till I get full confidence. If not, I will try your patch. Thanks > > --- x/include/linux/workqueue.h > +++ y/include/linux/workqueue.h > @@ -402,6 +402,7 @@ enum wq_flags { > */ > WQ_POWER_EFFICIENT = 1 << 7, > > + __WQ_INITIALIZING = 1 << 14, /* internal: workqueue is initializing */ > __WQ_DESTROYING = 1 << 15, /* internal: workqueue is destroying */ > __WQ_DRAINING = 1 << 16, /* internal: workqueue is draining */ > __WQ_ORDERED = 1 << 17, /* internal: workqueue is ordered */ > --- x/kernel/workqueue.c > +++ y/kernel/workqueue.c > @@ -5080,6 +5080,8 @@ static void pwq_release_workfn(struct kt > * is gonna access it anymore. Schedule RCU free. > */ > if (is_last) { > + if (wq->flags & __WQ_INITIALIZING) > + return; > wq_unregister_lockdep(wq); > call_rcu(&wq->rcu, rcu_free_wq); > } > @@ -5714,8 +5716,10 @@ struct workqueue_struct *alloc_workqueue > goto err_unreg_lockdep; > } > > + wq->flags |= __WQ_INITIALIZING; > if (alloc_and_link_pwqs(wq) < 0) > goto err_free_node_nr_active; > + wq->flags &= ~__WQ_INITIALIZING; > > if (wq_online && init_rescuer(wq) < 0) > goto err_destroy; > -- >