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Mon, 17 Aug 2020 05:43:06 +0000 From: Song Liu To: Hugh Dickins CC: Andrew Morton , "Kirill A. Shutemov" , Srikar Dronamraju , Oleg Nesterov , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" Subject: Re: [PATCH] uprobes: __replace_page() avoid BUG in munlock_vma_page() Thread-Topic: [PATCH] uprobes: __replace_page() avoid BUG in munlock_vma_page() Thread-Index: AQHWdA4T+6PyWIZ5c0iaUFwxmwC/66k7ynEA Date: Mon, 17 Aug 2020 05:43:06 +0000 Message-ID: <852258AE-75B6-404A-B236-9EEF37AEE43F@fb.com> References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3608.80.23.2.2) authentication-results: google.com; dkim=none (message not signed) header.d=none;google.com; dmarc=none action=none header.from=fb.com; x-originating-ip: [2620:10d:c090:400::5:91bd] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: b3c27ef0-69d5-4299-66a0-08d842706a8c x-ms-traffictypediagnostic: BYAPR15MB2648: x-microsoft-antispam-prvs: x-fb-source: Internal x-ms-oob-tlc-oobclassifiers: OLM:8882; x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: ecevC9ucLvoERdhM2PZBXuRx/Kbj5tT/tpGqNvFn1pemYXVQBp7TtVPoQqWRx8CWqZwqC4TaKdthifpnYVy33pX2j4A5f1g/xw9c7g95btP3RWuhnZwgiVx2+qucXNsXJFkTFVpIdV5CZB1+beaZbC/aJBVyP0IXuz6I/MJu2EWFlr2/uymfU1B7jTr0AzQeMXgWI+D6Jofz0sbCRoBGYU00spBo3FZChFVi6/vz6c033oyAs553GWu4gXLk548sZbvkOigidQdqeyGHWj2purVLWQEvaryxGW4gpSugLZhHfCAbeaaA08m5FM5aKzoVS688tSkBkVadKWFU9fwCmg== x-forefront-antispam-report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BYAPR15MB2999.namprd15.prod.outlook.com;PTR:;CAT:NONE;SFS:(396003)(136003)(376002)(346002)(39860400002)(366004)(2616005)(6512007)(5660300002)(6506007)(36756003)(4326008)(33656002)(186003)(71200400001)(8936002)(478600001)(2906002)(53546011)(66446008)(64756008)(66476007)(83380400001)(8676002)(86362001)(66946007)(54906003)(76116006)(6916009)(66556008)(6486002)(316002);DIR:OUT;SFP:1102; x-ms-exchange-antispam-messagedata: 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 x-ms-exchange-transport-forked: True Content-Type: text/plain; charset="us-ascii" Content-ID: <8B06E2BB002CA343B09060B57D593E0E@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB2999.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: b3c27ef0-69d5-4299-66a0-08d842706a8c X-MS-Exchange-CrossTenant-originalarrivaltime: 17 Aug 2020 05:43:06.1823 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: +7sy4JzPBw81GDE8wVuEGk8YIdSeyae2DfZCSPKhhuLpFpeHxeqKIk+uqyt7sQGGq+Gm/8Ow0UKSnWjuUonQ5g== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2648 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-08-17_02:2020-08-17,2020-08-17 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxscore=0 clxscore=1011 mlxlogscore=952 spamscore=0 phishscore=0 bulkscore=0 suspectscore=0 malwarescore=0 impostorscore=0 adultscore=0 lowpriorityscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008170046 X-FB-Internal: deliver X-Rspamd-Queue-Id: F3ACA18086E28 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > On Aug 16, 2020, at 1:44 PM, Hugh Dickins wrote: >=20 > syzbot crashed on the VM_BUG_ON_PAGE(PageTail) in munlock_vma_page(), > when called from uprobes __replace_page(). Which of many ways to fix it? > Settled on not calling when PageCompound (since Head and Tail are equals > in this context, PageCompound the usual check in uprobes.c, and the prior > use of FOLL_SPLIT_PMD will have cleared PageMlocked already). >=20 > Reported-by: syzbot > Fixes: 5a52c9df62b4 ("uprobe: use FOLL_SPLIT_PMD instead of FOLL_SPLIT") > Signed-off-by: Hugh Dickins > Cc: stable@vger.kernel.org # v5.4+ > --- > This one is not a 5.9-rc regression, but still good to fix. >=20 > kernel/events/uprobes.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) >=20 > --- v5.9-rc/kernel/events/uprobes.c 2020-08-12 19:46:50.851196584 -0700 > +++ linux/kernel/events/uprobes.c 2020-08-16 13:18:35.292821674 -0700 > @@ -205,7 +205,7 @@ static int __replace_page(struct vm_area > try_to_free_swap(old_page); > page_vma_mapped_walk_done(&pvmw); >=20 > - if (vma->vm_flags & VM_LOCKED) > + if ((vma->vm_flags & VM_LOCKED) && !PageCompound(old_page)) Do we need munlock_vma_page() for THP page head?=20 Thanks, Song > munlock_vma_page(old_page); > put_page(old_page); >=20