Commit dba58d3b authored by Mike Kravetz's avatar Mike Kravetz Committed by Linus Torvalds

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: default avatarMike Kravetz <>
Acked-by: default avatarMichal Hocko <>
Cc: Andrea Arcangeli <>
Cc: Aaron Lu <>
Cc: "Kirill A . Shutemov" <>
Cc: Vlastimil Babka <>
Cc: Anshuman Khandual <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 10903027
......@@ -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);
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment