From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) (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 E707B20B22 for ; Thu, 28 Aug 2025 09:24:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.190 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756373079; cv=none; b=M03M3BNKKlNvZNaL7DojXLkFGrBQpSih1Mhl9YDqBQ8kz8oPjcfzFl05gTJw7e2/eorumzeF9+4Fa81q5IpJvAeoLqJ5htRe0mziN42l8nE3sPmR9MH57tn/oWM0DSw8FG8TE1I0hJ8xKy8zmtzpELxMm7xqTF1SmXCNvkzlySY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756373079; c=relaxed/simple; bh=cAMBpNEnqZBUMOZijFi0Wg0qpCRAYmjnSgUaC98oFLM=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=OSGCy9ucLc/CgVk89jOOAPrSK2QflZmFOit3JEY//5IPMKO8e0i14WauFq1wsXVVfRv5FzzEWXqAcrCHGaT2Uak+MBGRnit1lTtRu9Mep8QRZJ5f3kAbf7Llt0VC8r8HAJR4LmkQhvtkAPmEGtHgRptUXrV9cAxbKUXgjQeBCSM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.190 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.88.214]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4cCG823FhNz2CgB1; Thu, 28 Aug 2025 17:20:02 +0800 (CST) Received: from dggpemf500016.china.huawei.com (unknown [7.185.36.197]) by mail.maildlp.com (Postfix) with ESMTPS id C425A1A016C; Thu, 28 Aug 2025 17:24:28 +0800 (CST) Received: from [10.174.176.70] (10.174.176.70) by dggpemf500016.china.huawei.com (7.185.36.197) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Thu, 28 Aug 2025 17:24:27 +0800 Message-ID: Date: Thu, 28 Aug 2025 17:24:26 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] pps: fix warning in pps_register_cdev when register device fail To: Calvin Owens CC: , , , , , References: <20250827065010.3208525-1-wangliang74@huawei.com> From: Wang Liang In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: kwepems100002.china.huawei.com (7.221.188.206) To dggpemf500016.china.huawei.com (7.185.36.197) 在 2025/8/27 23:32, Calvin Owens 写道: > On Wednesday 08/27 at 14:50 +0800, Wang Liang wrote: >> Similar to previous commit 2a934fdb01db ("media: v4l2-dev: fix error >> handling in __video_register_device()"), the release hook should be set >> before device_register(). Otherwise, when device_register() return error >> and put_device() try to callback the release function, the below warning >> may happen. >> >> ------------[ cut here ]------------ >> WARNING: CPU: 1 PID: 4760 at drivers/base/core.c:2567 device_release+0x1bd/0x240 drivers/base/core.c:2567 >> Modules linked in: >> CPU: 1 UID: 0 PID: 4760 Comm: syz.4.914 Not tainted 6.17.0-rc3+ #1 NONE >> RIP: 0010:device_release+0x1bd/0x240 drivers/base/core.c:2567 >> Call Trace: >> >> kobject_cleanup+0x136/0x410 lib/kobject.c:689 >> kobject_release lib/kobject.c:720 [inline] >> kref_put include/linux/kref.h:65 [inline] >> kobject_put+0xe9/0x130 lib/kobject.c:737 >> put_device+0x24/0x30 drivers/base/core.c:3797 >> pps_register_cdev+0x2da/0x370 drivers/pps/pps.c:402 >> pps_register_source+0x2f6/0x480 drivers/pps/kapi.c:108 >> pps_tty_open+0x190/0x310 drivers/pps/clients/pps-ldisc.c:57 >> tty_ldisc_open+0xa7/0x120 drivers/tty/tty_ldisc.c:432 >> tty_set_ldisc+0x333/0x780 drivers/tty/tty_ldisc.c:563 >> tiocsetd drivers/tty/tty_io.c:2429 [inline] >> tty_ioctl+0x5d1/0x1700 drivers/tty/tty_io.c:2728 >> vfs_ioctl fs/ioctl.c:51 [inline] >> __do_sys_ioctl fs/ioctl.c:598 [inline] >> __se_sys_ioctl fs/ioctl.c:584 [inline] >> __x64_sys_ioctl+0x194/0x210 fs/ioctl.c:584 >> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] >> do_syscall_64+0x5f/0x2a0 arch/x86/entry/syscall_64.c:94 >> entry_SYSCALL_64_after_hwframe+0x76/0x7e >> >> >> Before commit c79a39dc8d06 ("pps: Fix a use-after-free"), >> pps_register_cdev() call device_create() to create pps->dev, which will >> init dev->release to device_create_release(). Now the comment is outdated, >> just remove it. > Hi Wang, > > I'm curious why pps_register_cdev() is failing, is there possibly a > second issue to investigate there? Or was it fault injection? I find this issue from my local syzkaller project. Function pps_register_cdev() call the universal interface 'device_register', which can return error when kzalloc fail, or sysfs error, etc. Hope the above information is helpful. ------ Best regards Wang Liang > > Otherwise, makes perfect sense to me. I'm new to this code, so grain of > salt, but since I exposed it: > > Reviewed-by: Calvin Owens > > Thanks, > Calvin > >> Fixes: c79a39dc8d06 ("pps: Fix a use-after-free") >> Signed-off-by: Wang Liang >> --- >> drivers/pps/pps.c | 4 +--- >> 1 file changed, 1 insertion(+), 3 deletions(-) >> >> diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c >> index 9463232af8d2..0d2d57250575 100644 >> --- a/drivers/pps/pps.c >> +++ b/drivers/pps/pps.c >> @@ -383,13 +383,11 @@ int pps_register_cdev(struct pps_device *pps) >> pps->dev.devt = MKDEV(pps_major, pps->id); >> dev_set_drvdata(&pps->dev, pps); >> dev_set_name(&pps->dev, "pps%d", pps->id); >> + pps->dev.release = pps_device_destruct; >> err = device_register(&pps->dev); >> if (err) >> goto free_idr; >> >> - /* Override the release function with our own */ >> - pps->dev.release = pps_device_destruct; >> - >> pr_debug("source %s got cdev (%d:%d)\n", pps->info.name, pps_major, >> pps->id); >> >> -- >> 2.33.0 >>