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Fri, 12 Jun 2026 02:19:53 +0000 Message-ID: <44a31716-c021-463e-aa2b-8fdbe0b6b6a2@intel.com> Date: Thu, 11 Jun 2026 19:19:51 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/process: Return early on NULL iobm in native_tss_update_io_bitmap() To: lirongqing , Thomas Gleixner , "Ingo Molnar" , Borislav Petkov , Dave Hansen , , "H . Peter Anvin" , References: <20260601053715.2233-1-lirongqing@baidu.com> Content-Language: en-US From: Sohil Mehta In-Reply-To: <20260601053715.2233-1-lirongqing@baidu.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SJ0PR03CA0367.namprd03.prod.outlook.com (2603:10b6:a03:3a1::12) To DS0PR11MB7997.namprd11.prod.outlook.com (2603:10b6:8:125::14) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS0PR11MB7997:EE_|MW5PR11MB5859:EE_ X-MS-Office365-Filtering-Correlation-Id: e3be5f49-412a-43e5-9bd3-08dec82916a4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|23010399003|376014|366016|22082099003|18002099003|11063799006|56012099006; X-Microsoft-Antispam-Message-Info: SPW4XhxHe7Dh6nejQYKss+/dPSYVGBnBmTqaZoJasML/aqVL87ZlZnAzLtUcc0o+zSDXyTMgOXQvm20e9hrKRjK5SDu/7QqChVlWVELmSv2IAMg925TtHfFKLlQwrrejQoKlYQEfNdz0J35KNxIluLEN2kgZfduODpEmHAeRWKO9k9CV/2fvWFhYcL6j44TzezZ6mhB6jlSuymjND20C6uk0bvNytwMs2hsVGDQJ2E/NMEIcM0MvcVNWjbJLyL2DMMB7UkB2mNNtE2jE5ttROth13jE9d4HwIxeXk+jpzrfHClSSTsS8gtXaYX7Y45KDr597p4qwdKL8K2vUSMVZ+l11xeTbXh68mTY4KvAUHSokjofcV8TwW/kCNcEge9ZD557x0L7DGa1izoVv+zaW6UlIxOKdOknJ3ekD/XLIeFksV7sG9tOBCXolWdpdqW4oRzd1B/OfXdgKcCkzHiD4jTE9BXqxPB/+Hc1Lmj56ZgYe9ybt6zKO480dLi+7XyUXSSS4gNZVRVbyWK/BjmGAMXfnS/3/JwVhQxd2Jk13cRNR2A3MFLpKAWG7VGE8F/EAp3/SzvKeOPH78EDz28ChzTQAgNOkV9HSS1IVhpSxk5rGf2j4ws7TGB4NKGdqdGrj++b/mtuSWT4neLlENZUmA3NReZs9BFiDtvSHWON+lqbwjrDJVnhAv/lM3LM6LGWn X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS0PR11MB7997.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(23010399003)(376014)(366016)(22082099003)(18002099003)(11063799006)(56012099006);DIR:OUT;SFP:1101; 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Would it be better to say: Outside the IOPL emulation path, the IO bitmap is always expected to be allocated when TIF_IO_BITMAP is set. The paranoid WARN_ON_ONCE() handles the case where the flag and the pointer got out of sync. In this rare scenario, return early instead of continuing and dereferencing a NULL pointer. > Add a missing return statement to prevent a potential kernel NULL > pointer dereference panic. > > Signed-off-by: Li RongQing > --- > arch/x86/kernel/process.c | 1 + > 1 file changed, 1 insertion(+) > The code change looks good to me. Reviewed-by: Sohil Mehta > diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c > index 4c718f8..d5cd217 100644 > --- a/arch/x86/kernel/process.c > +++ b/arch/x86/kernel/process.c > @@ -486,6 +486,7 @@ void native_tss_update_io_bitmap(void) > if (WARN_ON_ONCE(!iobm)) { > clear_thread_flag(TIF_IO_BITMAP); > native_tss_invalidate_io_bitmap(); > + return; > } > > /*