From patchwork Tue Nov 12 00:06:45 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Hubbard X-Patchwork-Id: 11238261 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 77FFE1864 for ; Tue, 12 Nov 2019 00:09:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 562DF20840 for ; Tue, 12 Nov 2019 00:09:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="SJ2uh291" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727451AbfKLAHT (ORCPT ); Mon, 11 Nov 2019 19:07:19 -0500 Received: from hqemgate16.nvidia.com ([216.228.121.65]:3297 "EHLO hqemgate16.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726949AbfKLAHS (ORCPT ); Mon, 11 Nov 2019 19:07:18 -0500 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqemgate16.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Mon, 11 Nov 2019 16:06:16 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Mon, 11 Nov 2019 16:07:12 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Mon, 11 Nov 2019 16:07:12 -0800 Received: from HQMAIL107.nvidia.com (172.20.187.13) by HQMAIL105.nvidia.com (172.20.187.12) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 12 Nov 2019 00:07:12 +0000 Received: from rnnvemgw01.nvidia.com (10.128.109.123) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3 via Frontend Transport; Tue, 12 Nov 2019 00:07:11 +0000 Received: from blueforge.nvidia.com (Not Verified[10.110.48.28]) by rnnvemgw01.nvidia.com with Trustwave SEG (v7,5,8,10121) id ; Mon, 11 Nov 2019 16:07:11 -0800 From: John Hubbard To: Andrew Morton CC: Al Viro , Alex Williamson , Benjamin Herrenschmidt , =?utf-8?b?QmrDtnJuIFQ=?= =?utf-8?b?w7ZwZWw=?= , Christoph Hellwig , Dan Williams , Daniel Vetter , Dave Chinner , David Airlie , "David S . Miller" , Ira Weiny , Jan Kara , Jason Gunthorpe , Jens Axboe , Jonathan Corbet , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Magnus Karlsson , Mauro Carvalho Chehab , Michael Ellerman , Michal Hocko , Mike Kravetz , Paul Mackerras , Shuah Khan , Vlastimil Babka , , , , , , , , , , , , , LKML , John Hubbard Subject: [PATCH v3 08/23] vfio, mm: fix get_user_pages_remote() and FOLL_LONGTERM Date: Mon, 11 Nov 2019 16:06:45 -0800 Message-ID: <20191112000700.3455038-9-jhubbard@nvidia.com> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191112000700.3455038-1-jhubbard@nvidia.com> References: <20191112000700.3455038-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1573517177; bh=LHd6nlstYt/+WO2arS2xO7M4BDaQ4oXhsosl4/alSFg=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:X-NVConfidentiality: Content-Transfer-Encoding:Content-Type; b=SJ2uh291o0n2KAathWWaARa6MvN+m/A73UL04mBGFpYz9dwZwEu2YOKZK/z6oR36f S4MmrBohFcW7M4U4sGwLAQQaa4ErNxr5zszFsv1ppGBtK5nFe0oidXZ1r/1d+C5hHD 7OdWLPmiW5F6FVC/3nIr5wwa+GbS2yQdK9nseWpjIMdx642Wxvb5Kkid/PLVxBV3h0 OGPpdpsgYBaWnEIgbpCi7rX0MmoFtgOyBhqm3y6VOtt9bGAvDRddLo4gcp8LgfWb9W RGx06m/cZaFaW7nNL6zPl1lRK04yV8Qj7tUjurbVty1S8No3Te9OtVs5tQeXtoroeI mB7ag0CyWpHAw== Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org As it says in the updated comment in gup.c: current FOLL_LONGTERM behavior is incompatible with FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on vmas. However, the corresponding restriction in get_user_pages_remote() was slightly stricter than is actually required: it forbade all FOLL_LONGTERM callers, but we can actually allow FOLL_LONGTERM callers that do not set the "locked" arg. Update the code and comments accordingly, and update the VFIO caller to take advantage of this, fixing a bug as a result: the VFIO caller is logically a FOLL_LONGTERM user. Thanks to Jason Gunthorpe for pointing out a clean way to fix this. Suggested-by: Jason Gunthorpe Cc: Jerome Glisse Cc: Ira Weiny Signed-off-by: John Hubbard --- drivers/vfio/vfio_iommu_type1.c | 30 +++++++++++++----------------- mm/gup.c | 13 ++++++++----- 2 files changed, 21 insertions(+), 22 deletions(-) diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index d864277ea16f..017689b7c32b 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -348,24 +348,20 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr, flags |= FOLL_WRITE; down_read(&mm->mmap_sem); - if (mm == current->mm) { - ret = get_user_pages(vaddr, 1, flags | FOLL_LONGTERM, page, - vmas); - } else { - ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags, page, - vmas, NULL); - /* - * The lifetime of a vaddr_get_pfn() page pin is - * userspace-controlled. In the fs-dax case this could - * lead to indefinite stalls in filesystem operations. - * Disallow attempts to pin fs-dax pages via this - * interface. - */ - if (ret > 0 && vma_is_fsdax(vmas[0])) { - ret = -EOPNOTSUPP; - put_page(page[0]); - } + ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags | FOLL_LONGTERM, + page, vmas, NULL); + /* + * The lifetime of a vaddr_get_pfn() page pin is + * userspace-controlled. In the fs-dax case this could + * lead to indefinite stalls in filesystem operations. + * Disallow attempts to pin fs-dax pages via this + * interface. + */ + if (ret > 0 && vma_is_fsdax(vmas[0])) { + ret = -EOPNOTSUPP; + put_page(page[0]); } + up_read(&mm->mmap_sem); if (ret == 1) { diff --git a/mm/gup.c b/mm/gup.c index 933524de6249..cfe6dc5fc343 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1167,13 +1167,16 @@ long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm, struct vm_area_struct **vmas, int *locked) { /* - * FIXME: Current FOLL_LONGTERM behavior is incompatible with + * Current FOLL_LONGTERM behavior is incompatible with * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on - * vmas. As there are no users of this flag in this call we simply - * disallow this option for now. + * vmas. However, this only comes up if locked is set, and there are + * callers that do request FOLL_LONGTERM, but do not set locked. So, + * allow what we can. */ - if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM)) - return -EINVAL; + if (gup_flags & FOLL_LONGTERM) { + if (WARN_ON_ONCE(locked)) + return -EINVAL; + } return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas, locked,