Commit 325896ff authored by Dan Williams's avatar 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: default avatarHugh Dickins <hughd@google.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent a7de92da
......@@ -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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