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Tue, 18 Mar 2025 12:37:00 +0000 Received: from BYAPR12MB3205.namprd12.prod.outlook.com ([fe80::489:5515:fcf2:b991]) by BYAPR12MB3205.namprd12.prod.outlook.com ([fe80::489:5515:fcf2:b991%5]) with mapi id 15.20.8534.031; Tue, 18 Mar 2025 12:36:59 +0000 From: Stephen Eta Zhou To: David Disseldorp CC: "jsperbeck@google.com" , "akpm@linux-foundation.org" , "gregkh@linuxfoundation.org" , "lukas@wunner.de" , "wufan@linux.microsoft.com" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" Subject: Re: [RFC PATCH] initramfs: Add size validation to prevent tmpfs exhaustion Thread-Topic: [RFC PATCH] initramfs: Add size validation to prevent tmpfs exhaustion Thread-Index: AQHblJ3gvljUi14PpUKtURVssHl1u7N28UyAgAAdT5aAAQ5UAIAAVPUJgAA7kICAACpWmA== Date: Tue, 18 Mar 2025 12:36:59 +0000 Message-ID: References: <20250317182157.7adbc168.ddiss@suse.de> <20250318121424.614148e1.ddiss@suse.de> <20250318205139.71fe0c02.ddiss@suse.de> In-Reply-To: <20250318205139.71fe0c02.ddiss@suse.de> Accept-Language: en-US, zh-CN Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: msip_labels: x-ms-publictraffictype: Email x-ms-traffictypediagnostic: BYAPR12MB3205:EE_|SJ2PR12MB8181:EE_ x-ms-office365-filtering-correlation-id: 5aa285ce-9a4e-4fa6-e793-08dd661993d0 x-microsoft-antispam: BCL:0;ARA:14566002|461199028|15080799006|8062599003|19110799003|8060799006|15030799003|102099032|3412199025|440099028; 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charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-OriginatorOrg: outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: BYAPR12MB3205.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-RMS-PersistedConsumerOrg: 00000000-0000-0000-0000-000000000000 X-MS-Exchange-CrossTenant-Network-Message-Id: 5aa285ce-9a4e-4fa6-e793-08dd661993d0 X-MS-Exchange-CrossTenant-originalarrivaltime: 18 Mar 2025 12:36:59.6466 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 84df9e7f-e9f6-40af-b435-aaaaaaaaaaaa X-MS-Exchange-CrossTenant-rms-persistedconsumerorg: 00000000-0000-0000-0000-000000000000 X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ2PR12MB8181 =0A= > Not always. The *built-in* initramfs unpack_to_rootfs() error path=0A= > panics, but external initramfs unpack_to_rootfs() failure won't panic=0A= > immediately...=0A= =0A= You're right that the behavior differs between built-in and external initra= mfs handling. My concern is primarily about the built-in case, where unpack= _to_rootfs() will lead to a panic if decompression fails.=0A= =0A= > Are your console/serial drivers loaded as external modules? That sounds= =0A= > like a configuration problem.=0A= =0A= My console and serial port drivers are built into the kernel. I found that = if the built-in initramfs fails to be decompressed, it will enter a suspend= ed state when panic is called, and no logs will be output (my test environm= ent at this time does not have the early serial port). After debugging, I f= ound that console_flush_all did not seem to find an available console. I wi= ll debug this problem in depth next.=0A= =0A= Thanks,=0A= Stephen=0A= ________________________________________=0A= From:=A0David Disseldorp =0A= Sent:=A0Tuesday, March 18, 2025 17:51=0A= To:=A0Stephen Eta Zhou =0A= Cc:=A0jsperbeck@google.com ; akpm@linux-foundation.or= g ; gregkh@linuxfoundation.org ; lukas@wunner.de ; wufan@linux.microsoft.com <= wufan@linux.microsoft.com>; linux-kernel@vger.kernel.org ; linux-fsdevel@vger.kernel.org = =0A= Subject:=A0Re: [RFC PATCH] initramfs: Add size validation to prevent tmpfs = exhaustion=0A= =A0=0A= On Tue, 18 Mar 2025 06:28:53 +0000, Stephen Eta Zhou wrote:=0A= =0A= > > There's room for improvement WRT how out-of-memory failures are reporte= d=A0=0A= >=0A= > I am currently trying to find a good optimization solution for this. Sinc= e initramfs is decompressed in the early stage of the kernel, if the decomp= ression fails, it will call panic to put the kernel into a panic state.=0A= =0A= Not always. The *built-in* initramfs unpack_to_rootfs() error path=0A= panics, but external initramfs unpack_to_rootfs() failure won't panic=0A= immediately...=0A= =0A= > There is a contradiction: at this time, the console and serial port have = not been initialized yet, which will cause the error message to fail to be = output, resulting in a suspended state, and no valid output can be seen.=0A= =0A= Are your console/serial drivers loaded as external modules? That sounds=0A= like a configuration problem.=