Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Nadav Amit <namit@vmware.com>
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "x86@kernel.org" <x86@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>
Subject: Re: [PATCH] x86/ldt: Initialize the context lock for init_mm
Thread-Topic: [PATCH] x86/ldt: Initialize the context lock for init_mm
Thread-Index: AQHVMDMsFZ2Oh1rNP0yNtHzPaQvKzqa2CkqA
Date:   Mon, 1 Jul 2019 17:49:35 +0000
Message-ID: <D552F5D9-26A0-4584-8CEA-6E6E321D63E6@vmware.com>
References: <20190701173354.2pe62hhliok2afea@linutronix.de>
In-Reply-To: <20190701173354.2pe62hhliok2afea@linutronix.de>
Accept-Language: en-US
Content-Language: en-US
received-spf: None (protection.outlook.com: vmware.com does not designate
 permitted sender hosts)
Content-Type: text/plain; charset="us-ascii"
Content-ID: <659F74EEF4D4E04784D1D61F162E2EA7@namprd05.prod.outlook.com>
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: 038ef42a-e921-494b-0df4-08d6fe4c7b47
X-MS-Exchange-CrossTenant-originalarrivaltime: 01 Jul 2019 17:49:35.6968
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: b39138ca-3cee-4b4a-a4d6-cd83d9dd62f0
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: namit@vmware.com
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR05MB4437
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

> On Jul 1, 2019, at 10:33 AM, Sebastian Andrzej Siewior <bigeasy@linutroni=
x.de> wrote:
>=20
> The mutex mm->context->lock for init_mm is not initialized for init_mm.
> This wasn't a problem because it remained unused. This changed however
> since commit
> 	4fc19708b165c ("x86/alternatives: Initialize temporary mm for patching")
>=20
> Initialize the mutex for init_mm.
>=20
> Fixes: 4fc19708b165c ("x86/alternatives: Initialize temporary mm for patc=
hing")
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>=20
> The rwsem `ldt_usr_sem' is also not initialized for init_mm. No idea if
> we want this.

I cannot see why not (but it would need to depend on CONFIG_MODIFY_LDT_SYSC=
ALL)

>=20
> arch/x86/include/asm/mmu.h | 1 +
> 1 file changed, 1 insertion(+)
>=20
> diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
> index 5ff3e8af2c205..e78c7db878018 100644
> --- a/arch/x86/include/asm/mmu.h
> +++ b/arch/x86/include/asm/mmu.h
> @@ -59,6 +59,7 @@ typedef struct {
> #define INIT_MM_CONTEXT(mm)						\
> 	.context =3D {							\
> 		.ctx_id =3D 1,						\
> +		.lock =3D __MUTEX_INITIALIZER(mm.context.lock),		\

Sorry for my mistake. Thanks for fixing it up. I find it useful to know how
the problem was found or what the impact was - helps me sometimes to avoid
causing similar bugs in the future.

Reviewed-by: Nadav Amit <namit@vmware.com>=