From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vlastimil Babka Subject: Re: [PATCH] mm/mremap: Fail map duplication attempts for private mappings Date: Thu, 13 Jul 2017 21:11:08 +0200 Message-ID: <4e921eb5-8741-3337-9a7d-5ec9473412da@suse.cz> References: <1499961495-8063-1-git-send-email-mike.kravetz@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1499961495-8063-1-git-send-email-mike.kravetz-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org> Content-Language: en-US Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Mike Kravetz , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: Andrew Morton , Andrea Arcangeli , Michal Hocko , Aaron Lu , "Kirill A . Shutemov" , Anshuman Khandual , Linux API List-Id: linux-api@vger.kernel.org [+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 Acked-by: Vlastimil Babka > --- > 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); > >