From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f51.google.com (mail-pa0-f51.google.com [209.85.220.51]) by kanga.kvack.org (Postfix) with ESMTP id E22BD6B0055 for ; Tue, 27 May 2014 06:31:36 -0400 (EDT) Received: by mail-pa0-f51.google.com with SMTP id kq14so8958837pab.38 for ; Tue, 27 May 2014 03:31:36 -0700 (PDT) Received: from mga03.intel.com (mga03.intel.com. [143.182.124.21]) by mx.google.com with ESMTP id xm4si18137658pbc.45.2014.05.27.03.31.35 for ; Tue, 27 May 2014 03:31:35 -0700 (PDT) From: "Kirill A. Shutemov" In-Reply-To: <1401166595-4792-1-git-send-email-vinayakm.list@gmail.com> References: <1401166595-4792-1-git-send-email-vinayakm.list@gmail.com> Subject: RE: [PATCH] mm: fix zero page check in vm_normal_page Content-Transfer-Encoding: 7bit Message-Id: <20140527103130.3A04BE009B@blue.fi.intel.com> Date: Tue, 27 May 2014 13:31:30 +0300 (EEST) Sender: owner-linux-mm@kvack.org List-ID: To: Vinayak Menon Cc: linux-mm@kvack.org, hannes@cmpxchg.org, mgorman@suse.de, riel@redhat.com, mingo@kernel.org, peterz@infradead.org, kirill.shutemov@linux.intel.com, akpm@linux-foundation.org Vinayak Menon wrote: > An issue was observed when a userspace task exits. > The page which hits error here is the zero page. > In zap_pte_range, vm_normal_page gets called, and it > returns a page address and not NULL, even though the > pte corresponds to zero pfn. In this case, > HAVE_PTE_SPECIAL is not set, and VM_MIXEDMAP is set > in vm_flags. In the case of VM_MIXEDMAP , only pfn_valid > is checked, and not is_zero_pfn. This results in > zero page being returned instead of NULL. > > BUG: Bad page map in process mediaserver pte:9dff379f pmd:9bfbd831 > page:c0ed8e60 count:1 mapcount:-1 mapping: (null) index:0x0 > page flags: 0x404(referenced|reserved) > addr:40c3f000 vm_flags:10220051 anon_vma: (null) mapping:d9fe0764 index:fd > vma->vm_ops->fault: (null) > vma->vm_file->f_op->mmap: binder_mmap+0x0/0x274 How do we get zero_pfn there. We shouldn't use zero page for file mappings. binder does some tricks? > CPU: 0 PID: 1463 Comm: mediaserver Tainted: G W 3.10.17+ #1 > [] (unwind_backtrace+0x0/0x11c) from [] (show_stack+0x10/0x14) > [] (show_stack+0x10/0x14) from [] (print_bad_pte+0x158/0x190) > [] (print_bad_pte+0x158/0x190) from [] (unmap_single_vma+0x2e4/0x598) > [] (unmap_single_vma+0x2e4/0x598) from [] (unmap_vmas+0x34/0x50) > [] (unmap_vmas+0x34/0x50) from [] (exit_mmap+0xc8/0x1e8) > [] (exit_mmap+0xc8/0x1e8) from [] (mmput+0x54/0xd0) > [] (mmput+0x54/0xd0) from [] (do_exit+0x360/0x990) > [] (do_exit+0x360/0x990) from [] (do_group_exit+0x84/0xc0) > [] (do_group_exit+0x84/0xc0) from [] (get_signal_to_deliver+0x4d4/0x548) > [] (get_signal_to_deliver+0x4d4/0x548) from [] (do_signal+0xa8/0x3b8) > > Signed-off-by: Vinayak Menon > --- > mm/memory.c | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 037b812..c9a5027 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -771,6 +771,8 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, > if (vma->vm_flags & VM_MIXEDMAP) { > if (!pfn_valid(pfn)) > return NULL; > + if (is_zero_pfn(pfn)) > + return NULL; > goto out; > } else { > unsigned long off; > -- > 1.7.6 > -- Kirill A. Shutemov -- 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