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

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Hugh notes in response to commit 4cb19355ea "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: 4cb19355ea ("device-dax: fail all private mapping attempts")
Reported-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Dan Williams 2016-12-06 17:03:35 -08:00
parent a7de92dac9
commit 325896ffdf
1 changed files with 1 additions and 1 deletions
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2
drivers/dax/dax.c
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@ -271,7 +271,7 @@ static int check_vma(struct dax_dev *dax_dev, struct vm_area_struct *vma,
return -ENXIO; return -ENXIO;
/* prevent private mappings from being established */ /* 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", dev_info(dev, "%s: %s: fail, attempted private mapping\n",
current->comm, func); current->comm, func);
return -EINVAL; return -EINVAL;