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x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linuxfoundation.org header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030959AbeCSSXL (ORCPT ); Mon, 19 Mar 2018 14:23:11 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:48774 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031363AbeCSSXH (ORCPT ); Mon, 19 Mar 2018 14:23:07 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Nate Watterson , Joerg Roedel , Sasha Levin Subject: [PATCH 4.9 117/241] iommu/iova: Fix underflow bug in __alloc_and_insert_iova_range Date: Mon, 19 Mar 2018 19:06:22 +0100 Message-Id: <20180319180756.045874894@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180319180751.172155436@linuxfoundation.org> References: <20180319180751.172155436@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Nate Watterson [ Upstream commit 5016bdb796b3726eec043ca0ce3be981f712c756 ] Normally, calling alloc_iova() using an iova_domain with insufficient pfns remaining between start_pfn and dma_limit will fail and return a NULL pointer. Unexpectedly, if such a "full" iova_domain contains an iova with pfn_lo == 0, the alloc_iova() call will instead succeed and return an iova containing invalid pfns. This is caused by an underflow bug in __alloc_and_insert_iova_range() that occurs after walking the "full" iova tree when the search ends at the iova with pfn_lo == 0 and limit_pfn is then adjusted to be just below that (-1). This (now huge) limit_pfn gives the impression that a vast amount of space is available between it and start_pfn and thus a new iova is allocated with the invalid pfn_hi value, 0xFFF.... . To rememdy this, a check is introduced to ensure that adjustments to limit_pfn will not underflow. This issue has been observed in the wild, and is easily reproduced with the following sample code. struct iova_domain *iovad = kzalloc(sizeof(*iovad), GFP_KERNEL); struct iova *rsvd_iova, *good_iova, *bad_iova; unsigned long limit_pfn = 3; unsigned long start_pfn = 1; unsigned long va_size = 2; init_iova_domain(iovad, SZ_4K, start_pfn, limit_pfn); rsvd_iova = reserve_iova(iovad, 0, 0); good_iova = alloc_iova(iovad, va_size, limit_pfn, true); bad_iova = alloc_iova(iovad, va_size, limit_pfn, true); Prior to the patch, this yielded: *rsvd_iova == {0, 0} /* Expected */ *good_iova == {2, 3} /* Expected */ *bad_iova == {-2, -1} /* Oh no... */ After the patch, bad_iova is NULL as expected since inadequate space remains between limit_pfn and start_pfn after allocating good_iova. Signed-off-by: Nate Watterson Signed-off-by: Joerg Roedel Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/iommu/iova.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/iommu/iova.c +++ b/drivers/iommu/iova.c @@ -138,7 +138,7 @@ static int __alloc_and_insert_iova_range break; /* found a free slot */ } adjust_limit_pfn: - limit_pfn = curr_iova->pfn_lo - 1; + limit_pfn = curr_iova->pfn_lo ? (curr_iova->pfn_lo - 1) : 0; move_left: prev = curr; curr = rb_prev(curr);