From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932413AbaBGLvb (ORCPT ); Fri, 7 Feb 2014 06:51:31 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:42168 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753467AbaBGLvX (ORCPT ); Fri, 7 Feb 2014 06:51:23 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Alex Williamson , David Woodhouse , Joerg Roedel , Andrew Morton , Linus Torvalds , Luis Henriques Subject: [PATCH 3.11 158/233] intel-iommu: fix off-by-one in pagetable freeing Date: Fri, 7 Feb 2014 11:46:17 +0000 Message-Id: <1391773652-25214-159-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.8.3.2 In-Reply-To: <1391773652-25214-1-git-send-email-luis.henriques@canonical.com> References: <1391773652-25214-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.11 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.11.10.4 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Alex Williamson commit 08336fd218e087cc4fcc458e6b6dcafe8702b098 upstream. dma_pte_free_level() has an off-by-one error when checking whether a pte is completely covered by a range. Take for example the case of attempting to free pfn 0x0 - 0x1ff, ie. 512 entries covering the first 2M superpage. The level_size() is 0x200 and we test: static void dma_pte_free_level(... ... if (!(0 > 0 || 0x1ff < 0 + 0x200)) { ... } Clearly the 2nd test is true, which means we fail to take the branch to clear and free the pagetable entry. As a result, we're leaking pagetables and failing to install new pages over the range. This was found with a PCI device assigned to a QEMU guest using vfio-pci without a VGA device present. The first 1M of guest address space is mapped with various combinations of 4K pages, but eventually the range is entirely freed and replaced with a 2M contiguous mapping. intel-iommu errors out with something like: ERROR: DMA PTE for vPFN 0x0 already set (to 5c2b8003 not 849c00083) In this case 5c2b8003 is the pointer to the previous leaf page that was neither freed nor cleared and 849c00083 is the superpage entry that we're trying to replace it with. Signed-off-by: Alex Williamson Cc: David Woodhouse Cc: Joerg Roedel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Luis Henriques --- drivers/iommu/intel-iommu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c index 40203ad..cae5a08 100644 --- a/drivers/iommu/intel-iommu.c +++ b/drivers/iommu/intel-iommu.c @@ -917,7 +917,7 @@ static void dma_pte_free_level(struct dmar_domain *domain, int level, /* If range covers entire pagetable, free it */ if (!(start_pfn > level_pfn || - last_pfn < level_pfn + level_size(level))) { + last_pfn < level_pfn + level_size(level) - 1)) { dma_clear_pte(pte); domain_flush_cache(domain, pte, sizeof(*pte)); free_pgtable_page(level_pte); -- 1.8.3.2