From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753286AbdLGRmO (ORCPT ); Thu, 7 Dec 2017 12:42:14 -0500 Received: from omzsmtpe02.verizonbusiness.com ([199.249.25.209]:16369 "EHLO omzsmtpe02.verizonbusiness.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932081AbdLGPtn (ORCPT ); Thu, 7 Dec 2017 10:49:43 -0500 From: alexander.levin@verizon.com Cc: Andrea Arcangeli , "Kirill A. Shutemov" , Andrew Morton , "Linus Torvalds" , alexander.levin@verizon.com X-Host: endeavour.tdc.vzwcorp.com To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" Subject: [PATCH AUTOSEL for 4.9 005/156] userfaultfd: shmem: __do_fault requires VM_FAULT_NOPAGE Thread-Topic: [PATCH AUTOSEL for 4.9 005/156] userfaultfd: shmem: __do_fault requires VM_FAULT_NOPAGE Thread-Index: AQHTb3LjTMfEAfX69ESHUJ9bMDSBDA== Date: Thu, 7 Dec 2017 15:48:55 +0000 Message-ID: <20171207154845.4814-5-alexander.levin@verizon.com> References: <20171207154845.4814-1-alexander.levin@verizon.com> In-Reply-To: <20171207154845.4814-1-alexander.levin@verizon.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-messagesentrepresentingtype: 1 x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.144.60.250] Content-Type: text/plain; charset="iso-8859-1" MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id vB7HgIuS001227 From: Andrea Arcangeli [ Upstream commit 6bbc4a4144b1a69743022ac68dfaf6e7d993abb9 ] __do_fault assumes vmf->page has been initialized and is valid if VM_FAULT_NOPAGE is not returned by vma->vm_ops->fault(vma, vmf). handle_userfault() in turn should return VM_FAULT_NOPAGE if it doesn't return VM_FAULT_SIGBUS or VM_FAULT_RETRY (the other two possibilities). This VM_FAULT_NOPAGE case is only invoked when signal are pending and it didn't matter for anonymous memory before. It only started to matter since shmem was introduced. hugetlbfs also takes a different path and doesn't exercise __do_fault. Link: http://lkml.kernel.org/r/20170228154201.GH5816@redhat.com Signed-off-by: Andrea Arcangeli Reported-by: Dmitry Vyukov Cc: "Kirill A. Shutemov" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- fs/userfaultfd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index b86054cc41db..784d667475ae 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -419,7 +419,7 @@ int handle_userfault(struct fault_env *fe, unsigned long reason) * in such case. */ down_read(&mm->mmap_sem); - ret = 0; + ret = VM_FAULT_NOPAGE; } } -- 2.11.0