path: root/mm/mremap.c
diff options
authorMike Kravetz <mike.kravetz@oracle.com>2017-09-06 16:20:55 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-09-06 17:27:26 -0700
commitdba58d3b8c5045ad89c1c95d33d01451e3964db7 (patch)
tree39a5693fa2844a073a85be7ad9482fc4d55dfb51 /mm/mremap.c
parent10903027948d768d9639b31e9a555802e2dabafc (diff)
mm/mremap: fail map duplication attempts for private mappings
mremap will attempt to create a 'duplicate' mapping if old_size == 0 is specified. In the case of private mappings, mremap will actually create a fresh separate private mapping unrelated to the original. This does not fit with the design semantics of mremap as the intention is to create a new mapping based on the original. Therefore, return EINVAL in the case where an attempt is made to duplicate a private mapping. Also, print a warning message (once) if such an attempt is made. Link: http://lkml.kernel.org/r/cb9d9f6a-7095-582f-15a5-62643d65c736@oracle.com Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mremap.c')
1 files changed, 13 insertions, 0 deletions
diff --git a/mm/mremap.c b/mm/mremap.c
index 3f23715d3c69..7395564daa6c 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -384,6 +384,19 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
if (!vma || vma->vm_start > addr)
return ERR_PTR(-EFAULT);
+ /*
+ * !old_len is a special case where an attempt is made to 'duplicate'
+ * a mapping. This makes no sense for private mappings as it will
+ * instead create a fresh/new mapping unrelated to the original. This
+ * is contrary to the basic idea of mremap which creates new mappings
+ * based on the original. There are no known use cases for this
+ * behavior. As a result, fail such attempts.
+ */
+ if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
+ pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current->comm, current->pid);
+ return ERR_PTR(-EINVAL);
+ }
if (is_vm_hugetlb_page(vma))
return ERR_PTR(-EINVAL);