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

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 <[email protected]> know about it.

From: Dan Williams <[email protected]>
Date: Tue, 6 Dec 2016 17:03:35 -0800
Subject: device-dax: fix private mapping restriction, permit read-only

From: Dan Williams <[email protected]>

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.

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

@@ -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 [email protected] are

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