From patchwork Mon Dec 16 19:01:16 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Logan Gunthorpe X-Patchwork-Id: 11295055 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3EA971593 for ; Mon, 16 Dec 2019 19:01:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2625D2064B for ; Mon, 16 Dec 2019 19:01:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726454AbfLPTB0 (ORCPT ); Mon, 16 Dec 2019 14:01:26 -0500 Received: from ale.deltatee.com ([207.54.116.67]:34932 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725836AbfLPTBZ (ORCPT ); Mon, 16 Dec 2019 14:01:25 -0500 Received: from cgy1-donard.priv.deltatee.com ([172.16.1.31]) by ale.deltatee.com with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1igvcR-0005jD-3e; Mon, 16 Dec 2019 12:01:23 -0700 Received: from gunthorp by cgy1-donard.priv.deltatee.com with local (Exim 4.92) (envelope-from ) id 1igvcQ-0005Za-86; Mon, 16 Dec 2019 12:01:22 -0700 From: Logan Gunthorpe To: linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org, Vinod Koul Cc: Dan Williams , Dave Jiang , Kit Chow , Logan Gunthorpe Date: Mon, 16 Dec 2019 12:01:16 -0700 Message-Id: <20191216190120.21374-2-logang@deltatee.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191216190120.21374-1-logang@deltatee.com> References: <20191216190120.21374-1-logang@deltatee.com> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 172.16.1.31 X-SA-Exim-Rcpt-To: linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org, vkoul@kernel.org, dan.j.williams@intel.com, dave.jiang@intel.com, kchow@gigaio.com, logang@deltatee.com X-SA-Exim-Mail-From: gunthorp@deltatee.com X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on ale.deltatee.com X-Spam-Level: X-Spam-Status: No, score=-6.7 required=5.0 tests=ALL_TRUSTED,BAYES_00, MYRULES_NO_TEXT autolearn=no autolearn_force=no version=3.4.2 Subject: [PATCH 1/5] dmaengine: Store module owner in dma_device struct X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org dma_chan_to_owner() dereferences the driver from the struct device to obtain the owner and call module_[get|put](). However, if the backing device is unbound before the dma_device is unregistered, the driver will be cleared and this will cause a NULL pointer dereference. Instead, store a pointer to the owner module in the dma_device struct so the module reference can be properly put when the channel is put, even if the backing device was destroyed first. This change helps to support a safer unbind of DMA engines. If the dma_device is unregistered in the driver's remove function, there's no guarantee that there are no existing clients and a users action may trigger the WARN_ONCE in dma_async_device_unregister() which is unlikely to leave the system in a consistent state. Instead, a better approach is to allow the backing driver to go away and fail any subsequent requests to it. Signed-off-by: Logan Gunthorpe --- drivers/dma/dmaengine.c | 4 +++- include/linux/dmaengine.h | 2 ++ 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c index 03ac4b96117c..4b604086b1b3 100644 --- a/drivers/dma/dmaengine.c +++ b/drivers/dma/dmaengine.c @@ -179,7 +179,7 @@ __dma_device_satisfies_mask(struct dma_device *device, static struct module *dma_chan_to_owner(struct dma_chan *chan) { - return chan->device->dev->driver->owner; + return chan->device->owner; } /** @@ -919,6 +919,8 @@ int dma_async_device_register(struct dma_device *device) return -EIO; } + device->owner = device->dev->driver->owner; + if (dma_has_cap(DMA_MEMCPY, device->cap_mask) && !device->device_prep_dma_memcpy) { dev_err(device->dev, "Device claims capability %s, but op is not defined\n", diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h index 8fcdee1c0cf9..13aa0abb71de 100644 --- a/include/linux/dmaengine.h +++ b/include/linux/dmaengine.h @@ -674,6 +674,7 @@ struct dma_filter { * @fill_align: alignment shift for memset operations * @dev_id: unique device ID * @dev: struct device reference for dma mapping api + * @owner: owner module (automatically set based on the provided dev) * @src_addr_widths: bit mask of src addr widths the device supports * Width is specified in bytes, e.g. for a device supporting * a width of 4 the mask should have BIT(4) set. @@ -737,6 +738,7 @@ struct dma_device { int dev_id; struct device *dev; + struct module *owner; u32 src_addr_widths; u32 dst_addr_widths;