From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Kravetz Subject: [PATCH v2] mm/mremap: Fail map duplication attempts for private mappings Date: Thu, 20 Jul 2017 13:37:59 -0700 Message-ID: <1500583079-26504-1-git-send-email-mike.kravetz@oracle.com> References: <20170720082058.GF9058@dhcp22.suse.cz> Return-path: In-Reply-To: <20170720082058.GF9058@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org To: linux-mm@kvack.org, Linux API , linux-kernel@vger.kernel.org Cc: Andrew Morton , Andrea Arcangeli , Michal Hocko , Aaron Lu , "Kirill A . Shutemov" , Vlastimil Babka , Anshuman Khandual , Mike Kravetz List-Id: linux-api@vger.kernel.org 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. Also, print a warning message (once) if such an attempt is made. Signed-off-by: Mike Kravetz --- mm/mremap.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/mm/mremap.c b/mm/mremap.c index cd8a1b1..949f6a7 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -383,6 +383,15 @@ 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))) { + 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); -- 2.7.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org