Commit 325896ff authored Dec 06, 2016 by Dan Williams

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



Hugh notes in response to commit 4cb19355 "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: <stable@vger.kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Pawel Lebioda <pawel.lebioda@intel.com>
Fixes: 4cb19355 ("device-dax: fail all private mapping attempts")
Reported-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

parent a7de92da

drivers/dax/dax.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -271,7 +271,7 @@ static int check_vma(struct dax_dev dax_dev, struct vm_area_struct vma,
		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;

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