linux-kernel - [PATCH 4.9 38/39] mm: fail get_vaddr_frames() for filesystem-dax mappings

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Message-Id: <20180226201645.332724931@linuxfoundation.org>
Date:   Mon, 26 Feb 2018 21:20:59 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Williams <dan.j.williams@...el.com>,
        Jan Kara <jack@...e.cz>, Inki Dae <inki.dae@...sung.com>,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        Joonyoung Shim <jy0922.shim@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        Christoph Hellwig <hch@....de>,
        Doug Ledford <dledford@...hat.com>,
        Hal Rosenstock <hal.rosenstock@...il.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Jeff Moyer <jmoyer@...hat.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Sean Hefty <sean.hefty@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.9 38/39] mm: fail get_vaddr_frames() for filesystem-dax mappings

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Williams <dan.j.williams@...el.com>

commit b7f0554a56f21fb3e636a627450a9add030889be upstream.

Until there is a solution to the dma-to-dax vs truncate problem it is
not safe to allow V4L2, Exynos, and other frame vector users to create
long standing / irrevocable memory registrations against filesytem-dax
vmas.

[dan.j.williams@...el.com: add comment for vma_is_fsdax() check in get_vaddr_frames(), per Jan]
  Link: http://lkml.kernel.org/r/151197874035.26211.4061781453123083667.stgit@dwillia2-desk3.amr.corp.intel.com
Link: http://lkml.kernel.org/r/151068939985.7446.15684639617389154187.stgit@dwillia2-desk3.amr.corp.intel.com
Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings")
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
Reviewed-by: Jan Kara <jack@...e.cz>
Cc: Inki Dae <inki.dae@...sung.com>
Cc: Seung-Woo Kim <sw0312.kim@...sung.com>
Cc: Joonyoung Shim <jy0922.shim@...sung.com>
Cc: Kyungmin Park <kyungmin.park@...sung.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Christoph Hellwig <hch@....de>
Cc: Doug Ledford <dledford@...hat.com>
Cc: Hal Rosenstock <hal.rosenstock@...il.com>
Cc: Jason Gunthorpe <jgg@...lanox.com>
Cc: Jeff Moyer <jmoyer@...hat.com>
Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc: Sean Hefty <sean.hefty@...el.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 mm/frame_vector.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- a/mm/frame_vector.c
+++ b/mm/frame_vector.c
@@ -52,6 +52,18 @@ int get_vaddr_frames(unsigned long start
 		ret = -EFAULT;
 		goto out;
 	}
+
+	/*
+	 * While get_vaddr_frames() could be used for transient (kernel
+	 * controlled lifetime) pinning of memory pages all current
+	 * users establish long term (userspace controlled lifetime)
+	 * page pinning. Treat get_vaddr_frames() like
+	 * get_user_pages_longterm() and disallow it for filesystem-dax
+	 * mappings.
+	 */
+	if (vma_is_fsdax(vma))
+		return -EOPNOTSUPP;
+
 	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
 		vec->got_ref = true;
 		vec->is_pfns = false;