Patch "device-dax: fix private mapping restriction, permit read-only" has been added to the 4.8-stable tree

Patch "device-dax: fix private mapping restriction, permit read-only" has been added to the 4.8-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    device-dax: fix private mapping restriction, permit read-only

to the 4.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     device-dax-fix-private-mapping-restriction-permit-read-only.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 325896ffdf90f7cbd59fb873b7ba20d60d1ddf3c Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@intel.com>
Date: Tue, 6 Dec 2016 17:03:35 -0800
Subject: device-dax: fix private mapping restriction, permit read-only

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

commit 325896ffdf90f7cbd59fb873b7ba20d60d1ddf3c upstream.

Hugh notes in response to commit 4cb19355ea19 "device-dax: fail all
private mapping attempts":

  "I think that is more restrictive than you intended: haven't tried, but I
  believe it rejects a PROT_READ, MAP_SHARED, O_RDONLY fd mmap, leaving no
  way to mmap /dev/dax without write permission to it."

Indeed it does restrict read-only mappings, switch to checking
VM_MAYSHARE, not VM_SHARED.

Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Pawel Lebioda <pawel.lebioda@intel.com>
Fixes: 4cb19355ea19 ("device-dax: fail all private mapping attempts")
Reported-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/dax/dax.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/dax/dax.c
+++ b/drivers/dax/dax.c
@@ -324,7 +324,7 @@ static int check_vma(struct dax_dev *dax
 		return -ENXIO;
 
 	/* prevent private mappings from being established */
-	if ((vma->vm_flags & VM_SHARED) != VM_SHARED) {
+	if ((vma->vm_flags & VM_MAYSHARE) != VM_MAYSHARE) {
 		dev_info(dev, "%s: %s: fail, attempted private mapping\n",
 				current->comm, func);
 		return -EINVAL;


Patches currently in stable-queue which might be from dan.j.williams@intel.com are

queue-4.8/device-dax-fix-private-mapping-restriction-permit-read-only.patch