Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
IronPort-SDR: oVU4T1XGTcg0vgwKph79JuCgPiCQAsFzDn2ur2BMgdduAWj0+/gXkLBdwh6miFGCjQoMBTKXCr
 mL2dKwFyo/PQ==
IronPort-SDR: ZB1qINnf4HChrZ7AeBEPumiTQfl9AXZjoCFSgxFZTk4/9+pjxuMJexXz+HEb2aqKt7nAfjetdu
 vDeEIYCZ0aUg==
From:   "Gross, Mark" <mark.gross@intel.com>
To:     "madhuparnabhowmik10@gmail.com" <madhuparnabhowmik10@gmail.com>,
        "arnd@arndb.de" <arnd@arndb.de>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "andrianov@ispras.ru" <andrianov@ispras.ru>,
        "ldv-project@linuxtesting.org" <ldv-project@linuxtesting.org>
Subject: RE: [PATCH] drivers: char: tlclk.c: Avoid data race between init and
 interrupt handler
Thread-Topic: [PATCH] drivers: char: tlclk.c: Avoid data race between init and
 interrupt handler
Thread-Index: AQHWFM3h1p9Jv8e1vE+gEoGsQuceyqh9dRzw
Date:   Fri, 17 Apr 2020 15:51:08 +0000
Message-ID: <MW3PR11MB474563294D1D37DCAA9910798ED90@MW3PR11MB4745.namprd11.prod.outlook.com>
References: <20200417153451.1551-1-madhuparnabhowmik10@gmail.com>
In-Reply-To: <20200417153451.1551-1-madhuparnabhowmik10@gmail.com>
Accept-Language: en-US
Content-Language: en-US
dlp-version: 11.2.0.6
dlp-product: dlpe-windows
dlp-reaction: no-action
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: 8b5f242f-d83f-437a-67b0-08d7e2e72550
X-MS-Exchange-CrossTenant-originalarrivaltime: 17 Apr 2020 15:51:08.5363
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: W9KKqGFJxO756Qmwou09UJJWgHCooVKVsyGIosqeslP76SC/+7w7TWpiBg/OlqyJLjRIMoRf0r6Mmfzoc1Z1cQ==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW3PR11MB4652
X-OriginatorOrg: intel.com
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Looks reasonable to me.
+1
Ack
--mark

> -----Original Message-----
> From: madhuparnabhowmik10@gmail.com <madhuparnabhowmik10@gmail.com>
> Sent: Friday, April 17, 2020 8:35 AM
> To: Gross, Mark <mark.gross@intel.com>; arnd@arndb.de;
> gregkh@linuxfoundation.org
> Cc: linux-kernel@vger.kernel.org; andrianov@ispras.ru; ldv-
> project@linuxtesting.org; Madhuparna Bhowmik
> <madhuparnabhowmik10@gmail.com>
> Subject: [PATCH] drivers: char: tlclk.c: Avoid data race between init and=
 interrupt
> handler
>=20
> From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
>=20
> After registering character device the file operation callbacks can be ca=
lled. The
> open callback registers interrupt handler.
> Therefore interrupt handler can execute in parallel with rest of the init=
 function. To
> avoid such data race initialize telclk_interrupt variable and struct alar=
m_events
> before registering character device.
>=20
> Found by Linux Driver Verification project (linuxtesting.org).
>=20
> Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
> ---
>  drivers/char/tlclk.c | 17 ++++++++++-------
>  1 file changed, 10 insertions(+), 7 deletions(-)
>=20
> diff --git a/drivers/char/tlclk.c b/drivers/char/tlclk.c index
> 6d81bb3bb503..896a3550fba9 100644
> --- a/drivers/char/tlclk.c
> +++ b/drivers/char/tlclk.c
> @@ -777,17 +777,21 @@ static int __init tlclk_init(void)  {
>  	int ret;
>=20
> +	telclk_interrupt =3D (inb(TLCLK_REG7) & 0x0f);
> +
> +	alarm_events =3D kzalloc( sizeof(struct tlclk_alarms), GFP_KERNEL);
> +	if (!alarm_events) {
> +		ret =3D -ENOMEM;
> +		goto out1;
> +	}
> +
>  	ret =3D register_chrdev(tlclk_major, "telco_clock", &tlclk_fops);
>  	if (ret < 0) {
>  		printk(KERN_ERR "tlclk: can't get major %d.\n", tlclk_major);
> +		kfree(alarm_events);
>  		return ret;
>  	}
>  	tlclk_major =3D ret;
> -	alarm_events =3D kzalloc( sizeof(struct tlclk_alarms), GFP_KERNEL);
> -	if (!alarm_events) {
> -		ret =3D -ENOMEM;
> -		goto out1;
> -	}
>=20
>  	/* Read telecom clock IRQ number (Set by BIOS) */
>  	if (!request_region(TLCLK_BASE, 8, "telco_clock")) { @@ -796,7 +800,6
> @@ static int __init tlclk_init(void)
>  		ret =3D -EBUSY;
>  		goto out2;
>  	}
> -	telclk_interrupt =3D (inb(TLCLK_REG7) & 0x0f);
>=20
>  	if (0x0F =3D=3D telclk_interrupt ) { /* not MCPBL0010 ? */
>  		printk(KERN_ERR "telclk_interrupt =3D 0x%x non-mcpbl0010 hw.\n",
> @@ -837,8 +840,8 @@ static int __init tlclk_init(void)
>  	release_region(TLCLK_BASE, 8);
>  out2:
>  	kfree(alarm_events);
> -out1:
>  	unregister_chrdev(tlclk_major, "telco_clock");
> +out1:
>  	return ret;
>  }
>=20
> --
> 2.17.1