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Sat, 3 Mar 2018 18:42:57 -0500 Received: from mail-by2nam03on0119.outbound.protection.outlook.com ([104.47.42.119]:12016 "EHLO NAM03-BY2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933741AbeCCWer (ORCPT ); Sat, 3 Mar 2018 17:34:47 -0500 From: Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" CC: Nate Watterson , Joerg Roedel , Sasha Levin Subject: [PATCH AUTOSEL for 4.9 123/219] iommu/iova: Fix underflow bug in __alloc_and_insert_iova_range Thread-Topic: [PATCH AUTOSEL for 4.9 123/219] iommu/iova: Fix underflow bug in __alloc_and_insert_iova_range Thread-Index: AQHTsz8L08V1DDph70mUi7bdTnlA/Q== Date: Sat, 3 Mar 2018 22:29:07 +0000 Message-ID: <20180303222716.26640-123-alexander.levin@microsoft.com> References: <20180303222716.26640-1-alexander.levin@microsoft.com> In-Reply-To: <20180303222716.26640-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;MW2PR2101MB1068;7:ZE0FVx3eT4i9cgMwEDBGY7hu+0RWGbXNZ3Mgk0e0VQc5SxGIo1zv/3Y+QLRAS3kuvI9ZJ7CgSZhrJMdB7IQUED2erOBGvvE+ZBsiePNSGmKC6Ryd//R6ogfen6+JpQZI8jL6vogO5ns142zQjTnqiuxdYjNE5NlZ2r5hsNLrDiMB1XnTUxKexpcjbQOJL6ySgkELNY5a8pKI4JKHsgH95hZHlBlifDnBt8bb1pWSAotkrH7Orh9h+CLMTSYEA+lz x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 49f274b3-148b-4e36-83c2-08d58156f578 x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(4534165)(4627221)(201703031133081)(201702281549075)(48565401081)(5600026)(4604075)(3008032)(2017052603307)(7193020);SRVR:MW2PR2101MB1068; 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x-microsoft-antispam-message-info: QHIparo8U0ymA174eJeqVZLMEE/AB5imH1oeFC/TQpPJbdK9DMXpNKBrY77TSf3o/TRoFJFgWmg/ebA4qGz23i8YljvvMpbHrRzqpLZKO8UfqFshlHKYiMNUdl3AImH6wFQrXVijdMtRfIyB3NUBLOSpiG+nbjSG+7cvL42u7UE= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: 49f274b3-148b-4e36-83c2-08d58156f578 X-MS-Exchange-CrossTenant-originalarrivaltime: 03 Mar 2018 22:29:07.5257 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR2101MB1068 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: 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 =3D=3D 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 =3D=3D 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 =3D kzalloc(sizeof(*iovad), GFP_KERNEL); struct iova *rsvd_iova, *good_iova, *bad_iova; unsigned long limit_pfn =3D 3; unsigned long start_pfn =3D 1; unsigned long va_size =3D 2; init_iova_domain(iovad, SZ_4K, start_pfn, limit_pfn); rsvd_iova =3D reserve_iova(iovad, 0, 0); good_iova =3D alloc_iova(iovad, va_size, limit_pfn, true); bad_iova =3D alloc_iova(iovad, va_size, limit_pfn, true); Prior to the patch, this yielded: *rsvd_iova =3D=3D {0, 0} /* Expected */ *good_iova =3D=3D {2, 3} /* Expected */ *bad_iova =3D=3D {-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 --- drivers/iommu/iova.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c index e23001bfcfee..f106fd9782bf 100644 --- a/drivers/iommu/iova.c +++ b/drivers/iommu/iova.c @@ -138,7 +138,7 @@ static int __alloc_and_insert_iova_range(struct iova_do= main *iovad, break; /* found a free slot */ } adjust_limit_pfn: - limit_pfn =3D curr_iova->pfn_lo - 1; + limit_pfn =3D curr_iova->pfn_lo ? (curr_iova->pfn_lo - 1) : 0; move_left: prev =3D curr; curr =3D rb_prev(curr); --=20 2.14.1