[+CC linux-api] On 07/13/2017 05:58 PM, Mike Kravetz wrote: > mremap will create a 'duplicate' mapping if old_size == 0 is > specified. Such duplicate mappings make no sense for private > mappings. If duplication is attempted for a private mapping, > mremap creates a separate private mapping unrelated to the > original mapping and makes no modifications to the original. > This is contrary to the purpose of mremap which should return > a mapping which is in some way related to the original. > > Therefore, return EINVAL in the case where if an attempt is > made to duplicate a private mapping. > > Signed-off-by: Mike Kravetz <mike.krav...@oracle.com>
Acked-by: Vlastimil Babka <vba...@suse.cz> > --- > mm/mremap.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/mm/mremap.c b/mm/mremap.c > index cd8a1b1..076f506 100644 > --- a/mm/mremap.c > +++ b/mm/mremap.c > @@ -383,6 +383,13 @@ 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 a mapping is 'duplicated'. > + * Do not allow this for private mappings. > + */ > + if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) > + return ERR_PTR(-EINVAL); > + > if (is_vm_hugetlb_page(vma)) > return ERR_PTR(-EINVAL); > >
