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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0AC5FC433FE for ; Mon, 11 Oct 2021 08:36:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E05C260F21 for ; Mon, 11 Oct 2021 08:36:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235184AbhJKIiX (ORCPT ); Mon, 11 Oct 2021 04:38:23 -0400 Received: from relay10.mail.gandi.net ([217.70.178.230]:40003 "EHLO relay10.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235166AbhJKIiR (ORCPT ); Mon, 11 Oct 2021 04:38:17 -0400 Received: (Authenticated sender: alexandre.belloni@bootlin.com) by relay10.mail.gandi.net (Postfix) with ESMTPSA id 42A83240018; Mon, 11 Oct 2021 08:36:15 +0000 (UTC) Date: Mon, 11 Oct 2021 10:36:15 +0200 From: Alexandre Belloni To: Yang Yingliang Cc: linux-kernel@vger.kernel.org, linux-rtc@vger.kernel.org, a.zummo@towertech.it Subject: Re: [PATCH 2/2] rtc: class: return error code when cdev_device_add() failed Message-ID: References: <20211011080302.1982894-1-yangyingliang@huawei.com> <20211011080302.1982894-2-yangyingliang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211011080302.1982894-2-yangyingliang@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/10/2021 16:03:02+0800, Yang Yingliang wrote: > I got a null-ptr-deref report when doing fault injection test: > > general protection fault, probably for non-canonical address 0xdffffc0000000022: 0000 [#1] SMP KASAN PTI > KASAN: null-ptr-deref in range [0x0000000000000110-0x0000000000000117] > CPU: 1 PID: 1028 Comm: 33 Not tainted 5.15.0-rc3-00111-gf5dad42ed4fe-dirty #481 2a70b3e6ca240b8638beac7ef491cce6183bbec7 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 > RIP: 0010:device_del+0x132/0xdc0 > Code: 48 c1 ea 03 80 3c 02 00 0f 85 4f 0c 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b 7b 48 4d 8d a7 10 01 00 00 4c 89 e2 48 c1 ea 03 <0f> b6 04 02 84 c0 74 06 0f 8e 7f 0a 00 00 45 0f b6 b7 10 01 00 00 > RSP: 0018:ffffc90002e876b8 EFLAGS: 00010206 > RAX: dffffc0000000000 RBX: ffff88801eb84000 RCX: ffffffff97227644 > RDX: 0000000000000022 RSI: ffff8880146a0000 RDI: 0000000000000002 > RBP: ffff88801eb84120 R08: fffffbfff349a60d R09: fffffbfff349a60d > R10: ffffc90002e876b8 R11: fffffbfff349a60c R12: 0000000000000110 > R13: 0000000000000001 R14: ffffc90002e87848 R15: 0000000000000000 > FS: 00007fa514973500(0000) GS:ffff888104600000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007fa51474ccb0 CR3: 000000002bcb0001 CR4: 0000000000770ee0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > PKRU: 55555554 > Call Trace: > ? write_comp_data+0x2a/0x90 > ? cleanup_glue_dir+0x260/0x260 > ? is_rtc_hctosys.isra.0+0xb9/0xf0 > ? rtc_proc_show+0x440/0x440 > ? rcu_read_lock_held_common+0xe/0xa0 > ? rcu_read_lock_sched_held+0x62/0xe0 > cdev_device_del+0x1a/0x80 > devm_rtc_unregister_device+0x37/0x80 > release_nodes+0xc3/0x3b0 > > If cdev_device_add() fails, 'dev->p' is not set, it causes > null-ptr-deref when calling cdev_device_del(), return error > code when cdev_device_add() failed to fix this. > > Reported-by: Hulk Robot > Fixes: 3068a254d5519 ("rtc: introduce new registration method") > Signed-off-by: Yang Yingliang > --- > drivers/rtc/class.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c > index 1f18c39a4b82..76422faee05b 100644 > --- a/drivers/rtc/class.c > +++ b/drivers/rtc/class.c > @@ -399,12 +399,14 @@ int __devm_rtc_register_device(struct module *owner, struct rtc_device *rtc) > rtc_dev_prepare(rtc); > > err = cdev_device_add(&rtc->char_dev, &rtc->dev); > - if (err) > + if (err) { > dev_warn(rtc->dev.parent, "failed to add char device %d:%d\n", > MAJOR(rtc->dev.devt), rtc->id); > - else > + return err; As the checkpatch warning indicates, registering the character device as always been optional. d5ed9177f64fe95d9de79e6504d41612d9127e8a is the commit you want to fix. > + } else { > dev_dbg(rtc->dev.parent, "char device (%d:%d)\n", > MAJOR(rtc->dev.devt), rtc->id); > + } > > rtc_proc_add_device(rtc); > > -- > 2.25.1 > -- Alexandre Belloni, co-owner and COO, Bootlin Embedded Linux and Kernel engineering https://bootlin.com