From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6EFFCC4332F for ; Tue, 22 Mar 2022 21:40:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230382AbiCVVlt (ORCPT ); Tue, 22 Mar 2022 17:41:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45088 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235878AbiCVVlM (ORCPT ); Tue, 22 Mar 2022 17:41:12 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 29BF0B849 for ; Tue, 22 Mar 2022 14:39:41 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id D0A9EB81D9E for ; Tue, 22 Mar 2022 21:39:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6F366C340EE; Tue, 22 Mar 2022 21:39:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1647985178; bh=P45jF2cSIC0S4zMQop2TdiAZmryr8wUTW/pvsxyxx14=; h=Date:To:From:In-Reply-To:Subject:From; b=afSn/VEm87CU/uVGxSVbSgBFWMT8Cg7UA4fd0cN8gnk4KlQrVrlJebFugoAG/sAqV djvh1lfjfF0+yUDURP0NIalVVQ28XBIFhK2GuF3RkxDNEBlOVHqlJQPjzJPkFPnbJ1 WadhmwsLqFT135E8eAZDb2o/bbEv78MbnVFqp1GU= Date: Tue, 22 Mar 2022 14:39:37 -0700 To: willy@infradead.org, lukas.bulwahn@gmail.com, kirill.shutemov@linux.intel.com, jhubbard@nvidia.com, jgg@ziepe.ca, jgg@nvidia.com, jack@suse.cz, imbrenda@linux.ibm.com, hch@lst.de, david@redhat.com, alex.williamson@redhat.com, aarcange@redhat.com, peterx@redhat.com, akpm@linux-foundation.org, patches@lists.linux.dev, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org From: Andrew Morton In-Reply-To: <20220322143803.04a5e59a07e48284f196a2f9@linux-foundation.org> Subject: [patch 022/227] mm: fix invalid page pointer returned with FOLL_PIN gups Message-Id: <20220322213938.6F366C340EE@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Peter Xu Subject: mm: fix invalid page pointer returned with FOLL_PIN gups Patch series "mm/gup: some cleanups", v5. This patch (of 5): Alex reported invalid page pointer returned with pin_user_pages_remote() from vfio after upstream commit 4b6c33b32296 ("vfio/type1: Prepare for batched pinning with struct vfio_batch"). It turns out that it's not the fault of the vfio commit; however after vfio switches to a full page buffer to store the page pointers it starts to expose the problem easier. The problem is for VM_PFNMAP vmas we should normally fail with an -EFAULT then vfio will carry on to handle the MMIO regions. However when the bug triggered, follow_page_mask() returned -EEXIST for such a page, which will jump over the current page, leaving that entry in **pages untouched. However the caller is not aware of it, hence the caller will reference the page as usual even if the pointer data can be anything. We had that -EEXIST logic since commit 1027e4436b6a ("mm: make GUP handle pfn mapping unless FOLL_GET is requested") which seems very reasonable. It could be that when we reworked GUP with FOLL_PIN we could have overlooked that special path in commit 3faa52c03f44 ("mm/gup: track FOLL_PIN pages"), even if that commit rightfully touched up follow_devmap_pud() on checking FOLL_PIN when it needs to return an -EEXIST. Attaching the Fixes to the FOLL_PIN rework commit, as it happened later than 1027e4436b6a. [jhubbard@nvidia.com: added some tags, removed a reference to an out of tree module.] Link: https://lkml.kernel.org/r/20220207062213.235127-1-jhubbard@nvidia.com Link: https://lkml.kernel.org/r/20220204020010.68930-1-jhubbard@nvidia.com Link: https://lkml.kernel.org/r/20220204020010.68930-2-jhubbard@nvidia.com Fixes: 3faa52c03f44 ("mm/gup: track FOLL_PIN pages") Signed-off-by: Peter Xu Signed-off-by: John Hubbard Reviewed-by: Claudio Imbrenda Reported-by: Alex Williamson Debugged-by: Alex Williamson Tested-by: Alex Williamson Reviewed-by: Christoph Hellwig Reviewed-by: Jan Kara Cc: Andrea Arcangeli Cc: Kirill A. Shutemov Cc: Jason Gunthorpe Cc: David Hildenbrand Cc: Lukas Bulwahn Cc: Matthew Wilcox (Oracle) Cc: Jason Gunthorpe Signed-off-by: Andrew Morton --- mm/gup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/gup.c~mm-fix-invalid-page-pointer-returned-with-foll_pin-gups +++ a/mm/gup.c @@ -465,7 +465,7 @@ static int follow_pfn_pte(struct vm_area pte_t *pte, unsigned int flags) { /* No page to get reference */ - if (flags & FOLL_GET) + if (flags & (FOLL_GET | FOLL_PIN)) return -EFAULT; if (flags & FOLL_TOUCH) { _