Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754627AbbGCOI2 (ORCPT ); Fri, 3 Jul 2015 10:08:28 -0400 Received: from mga11.intel.com ([192.55.52.93]:8473 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754918AbbGCOIS (ORCPT ); Fri, 3 Jul 2015 10:08:18 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.15,400,1432623600"; d="scan'208";a="740084259" From: "Kirill A. Shutemov" To: Andrew Morton , Linus Torvalds , Rik van Riel , Mel Gorman Cc: Hugh Dickins , Andrea Arcangeli , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, "Kirill A. Shutemov" Subject: [PATCH] mm: avoid setting up anonymous pages into file mapping Date: Fri, 3 Jul 2015 17:07:27 +0300 Message-Id: <1435932447-84377-1-git-send-email-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.1.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2113 Lines: 62 Reading page fault handler code I've noticed that under right circumstances kernel would map anonymous pages into file mappings: if the VMA doesn't have vm_ops->fault() and the VMA wasn't fully populated on ->mmap(), kernel would handle page fault to not populated pte with do_anonymous_page(). There's chance that it was done intentionally, but I don't see good justification for this. We just hide bugs in broken drivers. Let's change page fault handler to use do_anonymous_page() only on anonymous VMA (->vm_ops == NULL). For file mappings without vm_ops->fault() page fault on pte_none() entry would lead to SIGBUS. Signed-off-by: Kirill A. Shutemov --- mm/memory.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 8a2fc9945b46..f3ee782059e3 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3115,6 +3115,9 @@ static int do_fault(struct mm_struct *mm, struct vm_area_struct *vma, - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; pte_unmap(page_table); + + if (unlikely(!vma->vm_ops->fault)) + return VM_FAULT_SIGBUS; if (!(flags & FAULT_FLAG_WRITE)) return do_read_fault(mm, vma, address, pmd, pgoff, flags, orig_pte); @@ -3260,13 +3263,13 @@ static int handle_pte_fault(struct mm_struct *mm, barrier(); if (!pte_present(entry)) { if (pte_none(entry)) { - if (vma->vm_ops) { - if (likely(vma->vm_ops->fault)) - return do_fault(mm, vma, address, pte, - pmd, flags, entry); + if (!vma->vm_ops) { + return do_anonymous_page(mm, vma, address, pte, + pmd, flags); + } else { + return do_fault(mm, vma, address, pte, pmd, + flags, entry); } - return do_anonymous_page(mm, vma, address, - pte, pmd, flags); } return do_swap_page(mm, vma, address, pte, pmd, flags, entry); -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/