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[104.57.184.186]) by smtp.gmail.com with ESMTPSA id f7sm1609868oti.35.2022.01.10.10.55.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Jan 2022 10:55:20 -0800 (PST) Date: Mon, 10 Jan 2022 10:56:03 -0800 From: Bjorn Andersson To: Matthias Kaehlcke Cc: Andy Gross , Ohad Ben-Cohen , Stephen Boyd , linux-kernel@vger.kernel.org, linux-remoteproc@vger.kernel.org, Sibi Sankar , Sujit Kautkar , Mathieu Poirier Subject: Re: [PATCH v6 2/2] rpmsg: char: Fix race between the release of rpmsg_eptdev and cdev Message-ID: References: <20220110104706.v6.1.Iaac908f3e3149a89190ce006ba166e2d3fd247a3@changeid> <20220110104706.v6.2.Idde68b05b88d4a2e6e54766c653f3a6d9e419ce6@changeid> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220110104706.v6.2.Idde68b05b88d4a2e6e54766c653f3a6d9e419ce6@changeid> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 10 Jan 10:47 PST 2022, Matthias Kaehlcke wrote: > struct rpmsg_eptdev contains a struct cdev. The current code frees > the rpmsg_eptdev struct in rpmsg_eptdev_destroy(), but the cdev is > a managed object, therefore its release is not predictable and the > rpmsg_eptdev could be freed before the cdev is entirely released. > > The cdev_device_add/del() API was created to address this issue > (see commit 233ed09d7fda), use it instead of cdev add/del(). > > Fixes: c0cdc19f84a4 ("rpmsg: Driver for user space endpoint interface") > Suggested-by: Bjorn Andersson > Signed-off-by: Matthias Kaehlcke > Reviewed-by: Mathieu Poirier Reviewed-by: Bjorn Andersson Regards, Bjorn > --- > > Changes in v6: > - remove cdev_del() from rpmsg_eptdev_release_device() > - added 'Reviewed-by' tag from Mathieu and 'Suggested-by' tag > > Changes in v5: > - patch added to the series > > drivers/rpmsg/rpmsg_char.c | 11 ++--------- > 1 file changed, 2 insertions(+), 9 deletions(-) > > diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c > index ba85f5d11960..49dd5a200998 100644 > --- a/drivers/rpmsg/rpmsg_char.c > +++ b/drivers/rpmsg/rpmsg_char.c > @@ -92,7 +92,7 @@ static int rpmsg_eptdev_destroy(struct device *dev, void *data) > /* wake up any blocked readers */ > wake_up_interruptible(&eptdev->readq); > > - device_del(&eptdev->dev); > + cdev_device_del(&eptdev->cdev, &eptdev->dev); > put_device(&eptdev->dev); > > return 0; > @@ -335,7 +335,6 @@ static void rpmsg_eptdev_release_device(struct device *dev) > > ida_simple_remove(&rpmsg_ept_ida, dev->id); > ida_simple_remove(&rpmsg_minor_ida, MINOR(eptdev->dev.devt)); > - cdev_del(&eptdev->cdev); > kfree(eptdev); > } > > @@ -380,19 +379,13 @@ static int rpmsg_eptdev_create(struct rpmsg_ctrldev *ctrldev, > dev->id = ret; > dev_set_name(dev, "rpmsg%d", ret); > > - ret = cdev_add(&eptdev->cdev, dev->devt, 1); > + ret = cdev_device_add(&eptdev->cdev, &eptdev->dev); > if (ret) > goto free_ept_ida; > > /* We can now rely on the release function for cleanup */ > dev->release = rpmsg_eptdev_release_device; > > - ret = device_add(dev); > - if (ret) { > - dev_err(dev, "device_add failed: %d\n", ret); > - put_device(dev); > - } > - > return ret; > > free_ept_ida: > -- > 2.34.1.575.g55b058a8bb-goog >