From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f199.google.com (mail-qk0-f199.google.com [209.85.220.199]) by kanga.kvack.org (Postfix) with ESMTP id 7BEFB6B0038 for ; Mon, 16 Oct 2017 18:39:18 -0400 (EDT) Received: by mail-qk0-f199.google.com with SMTP id m189so17229766qke.21 for ; Mon, 16 Oct 2017 15:39:18 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id e88si5838624qtb.484.2017.10.16.15.39.17 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 16 Oct 2017 15:39:17 -0700 (PDT) From: Andrea Arcangeli Subject: [PATCH 1/1] userfaultfd: hugetlbfs: prevent UFFDIO_COPY to fill beyond the end of i_size Date: Tue, 17 Oct 2017 00:39:14 +0200 Message-Id: <20171016223914.2421-2-aarcange@redhat.com> In-Reply-To: <20171016223914.2421-1-aarcange@redhat.com> References: <20171016223914.2421-1-aarcange@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , linux-mm@kvack.org Cc: Mike Rapoport , "Dr. David Alan Gilbert" , Mike Kravetz kernel BUG at fs/hugetlbfs/inode.c:484! RIP: 0010:[] [] remove_inode_hugepages+0x3d0/0x410 Call Trace: [] hugetlbfs_setattr+0xd9/0x130 [] notify_change+0x292/0x410 [] ? security_inode_need_killpriv+0x16/0x20 [] do_truncate+0x65/0xa0 [] ? do_sys_ftruncate.constprop.3+0xe5/0x180 [] do_sys_ftruncate.constprop.3+0x11a/0x180 [] SyS_ftruncate+0xe/0x10 [] tracesys+0xd9/0xde This oops was caused by the lack of i_size check in hugetlb_mcopy_atomic_pte. mmap() can still succeed beyond the end of the i_size after vmtruncate zapped vmas in those ranges, but the faults must not succeed, and that includes UFFDIO_COPY. We could differentiate the retval to userland to represent a SIGBUS like a page fault would do (vs SIGSEGV), but it doesn't seem very useful and we'd need to pick a random retval as there's no meaningful syscall retval that would differentiate from SIGSEGV and SIGBUS, there's just -EFAULT. Reviewed-by: Mike Kravetz Signed-off-by: Andrea Arcangeli --- mm/hugetlb.c | 32 ++++++++++++++++++++++++++++++-- 1 file changed, 30 insertions(+), 2 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 357161bd1519..0cbb7c37dc33 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4012,6 +4012,9 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, unsigned long src_addr, struct page **pagep) { + struct address_space *mapping; + pgoff_t idx; + unsigned long size; int vm_shared = dst_vma->vm_flags & VM_SHARED; struct hstate *h = hstate_vma(dst_vma); pte_t _dst_pte; @@ -4049,13 +4052,24 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, __SetPageUptodate(page); __set_page_huge_active(page); + mapping = dst_vma->vm_file->f_mapping; + idx = vma_hugecache_offset(h, dst_vma, dst_addr); + /* * If shared, add to page cache */ if (vm_shared) { - struct address_space *mapping = dst_vma->vm_file->f_mapping; - pgoff_t idx = vma_hugecache_offset(h, dst_vma, dst_addr); + size = i_size_read(mapping->host) >> huge_page_shift(h); + ret = -EFAULT; + if (idx >= size) + goto out_release_nounlock; + /* + * Serialization between remove_inode_hugepages() and + * huge_add_to_page_cache() below happens through the + * hugetlb_fault_mutex_table that here must be hold by + * the caller. + */ ret = huge_add_to_page_cache(page, mapping, idx); if (ret) goto out_release_nounlock; @@ -4064,6 +4078,20 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, ptl = huge_pte_lockptr(h, dst_mm, dst_pte); spin_lock(ptl); + /* + * Recheck the i_size after holding PT lock to make sure not + * to leave any page mapped (as page_mapped()) beyond the end + * of the i_size (remove_inode_hugepages() is strict about + * enforcing that). If we bail out here, we'll also leave a + * page in the radix tree in the vm_shared case beyond the end + * of the i_size, but remove_inode_hugepages() will take care + * of it as soon as we drop the hugetlb_fault_mutex_table. + */ + size = i_size_read(mapping->host) >> huge_page_shift(h); + ret = -EFAULT; + if (idx >= size) + goto out_release_unlock; + ret = -EEXIST; if (!huge_pte_none(huge_ptep_get(dst_pte))) goto out_release_unlock; -- 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