From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.bootlin.com ([62.4.15.54]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1ew7W6-0006Ua-EE for linux-mtd@lists.infradead.org; Wed, 14 Mar 2018 14:36:36 +0000 Date: Wed, 14 Mar 2018 15:36:00 +0100 From: Boris Brezillon To: Arvind Yadav Cc: dwmw2@infradead.org, computersforpeace@gmail.com, boris.brezillon@free-electrons.com, marek.vasut@gmail.com, richard@nod.at, cyrille.pitchen@wedev4u.fr, dedekind1@gmail.com, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org Subject: Re: [PATCH 1/2] mtd: use put_device() if device_register fail Message-ID: <20180314153600.458c0fe4@bbrezillon> In-Reply-To: <39c4af723ea37cd05976a17cb9c1fbc975496ffd.1520592440.git.arvind.yadav.cs@gmail.com> References: <39c4af723ea37cd05976a17cb9c1fbc975496ffd.1520592440.git.arvind.yadav.cs@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, 9 Mar 2018 16:20:48 +0530 Arvind Yadav wrote: > if device_register() returned an error! Always use put_device() > to give up the reference initialized. > > Signed-off-by: Arvind Yadav > --- > drivers/mtd/mtdcore.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c > index 28553c8..4d77ca2 100644 > --- a/drivers/mtd/mtdcore.c > +++ b/drivers/mtd/mtdcore.c > @@ -586,6 +586,7 @@ int add_mtd_device(struct mtd_info *mtd) > return 0; > > fail_added: > + put_device(&mtd->dev); Not sure this is a good idea: the put_device() call will trigger an mtd_devtype->release(), which will in turn call device_destroy() on something that does not exist yet. Not sure if this is a real problem, but it does not look like the right thing to do. > of_node_put(mtd_get_of_node(mtd)); You're referencing an object that is supposed to have been freed/released by the put_device() call. Again, it's not really a problem because in our case ->release() does not free the mtd object (as is usually done in other parts of the kernel), but it still looks wrong. It's probably better to move the of_node_put() and the below idr_remove() call in the ->release() hook if you want to use put_device(). > idr_remove(&mtd_idr, i); > fail_locked: -- Boris Brezillon, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com