From patchwork Tue Jan 31 16:58:04 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Sistare X-Patchwork-Id: 13123180 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 08E17C636D3 for ; Tue, 31 Jan 2023 16:58:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231705AbjAaQ62 (ORCPT ); Tue, 31 Jan 2023 11:58:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34700 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231668AbjAaQ6U (ORCPT ); Tue, 31 Jan 2023 11:58:20 -0500 Received: from mx0b-00069f02.pphosted.com (mx0b-00069f02.pphosted.com [205.220.177.32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D7B0410274 for ; Tue, 31 Jan 2023 08:58:15 -0800 (PST) Received: from pps.filterd (m0246632.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 30VEDe17015116; Tue, 31 Jan 2023 16:58:12 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : in-reply-to : references; s=corp-2022-7-12; bh=ImLsktzwpPRLhY97K2/KK9U8hSaDxugCuR28I8wGkVU=; b=AeY8dW0Pv++K+BfxLBpYz58mB+sctLzr2LktShdiYuVB3LCStBqBSxyP/ptRry0xyqNy LejHhLqyOwmcxnUoyjBNwpv5tSGVf3W91t7GcTYCtARASQbSerOyxJKg3fUWA+/OISR5 abkHKqwhQVzoCxzCW7M4Suh690wXqkeX1U1NwKIpnDHZ81rbASqUhLa4gi50iMKTNXgi 8iF89KwX5RmUUb0s+3j5cZgk45eoieKVPm+ISOF7kBX7is9biB43mUaZznAERp2bjzwq SiRNx6XFuO5H08XMG/J+LaUZlg+RdEFwT5EopdY6tAGas2ppX/9I+efpydxHzpIV4mEf fg== Received: from phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (phxpaimrmta02.appoci.oracle.com [147.154.114.232]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 3ncvmhp4t8-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 31 Jan 2023 16:58:12 +0000 Received: from pps.filterd (phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (8.17.1.5/8.17.1.5) with ESMTP id 30VGXIJW025281; Tue, 31 Jan 2023 16:58:11 GMT Received: from pps.reinject (localhost [127.0.0.1]) by phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTPS id 3nct566vb0-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 31 Jan 2023 16:58:11 +0000 Received: from phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 30VGw98l002013; Tue, 31 Jan 2023 16:58:10 GMT Received: from ca-dev63.us.oracle.com (ca-dev63.us.oracle.com [10.211.8.221]) by phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTP id 3nct566v9x-3; Tue, 31 Jan 2023 16:58:10 +0000 From: Steve Sistare To: kvm@vger.kernel.org Cc: Alex Williamson , Cornelia Huck , Jason Gunthorpe , Kevin Tian , Steve Sistare Subject: [PATCH V8 2/7] vfio/type1: prevent underflow of locked_vm via exec() Date: Tue, 31 Jan 2023 08:58:04 -0800 Message-Id: <1675184289-267876-3-git-send-email-steven.sistare@oracle.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1675184289-267876-1-git-send-email-steven.sistare@oracle.com> References: <1675184289-267876-1-git-send-email-steven.sistare@oracle.com> X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.930,Hydra:6.0.562,FMLib:17.11.122.1 definitions=2023-01-31_08,2023-01-31_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 adultscore=0 suspectscore=0 mlxscore=0 spamscore=0 phishscore=0 bulkscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2301310150 X-Proofpoint-ORIG-GUID: 5Bo1j_V8fhmp4UwMn6QVTUlGI-zuKizT X-Proofpoint-GUID: 5Bo1j_V8fhmp4UwMn6QVTUlGI-zuKizT Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org When a vfio container is preserved across exec, the task does not change, but it gets a new mm with locked_vm=0, and loses the count from existing dma mappings. If the user later unmaps a dma mapping, locked_vm underflows to a large unsigned value, and a subsequent dma map request fails with ENOMEM in __account_locked_vm. To avoid underflow, grab and save the mm at the time a dma is mapped. Use that mm when adjusting locked_vm, rather than re-acquiring the saved task's mm, which may have changed. If the saved mm is dead, do nothing. locked_vm is incremented for existing mappings in a subsequent patch. Fixes: 73fa0d10d077 ("vfio: Type1 IOMMU implementation") Cc: stable@vger.kernel.org Signed-off-by: Steve Sistare Reviewed-by: Kevin Tian --- drivers/vfio/vfio_iommu_type1.c | 41 ++++++++++++++--------------------------- 1 file changed, 14 insertions(+), 27 deletions(-) diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index e8902e7..ee9e988 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -100,6 +100,7 @@ struct vfio_dma { struct task_struct *task; struct rb_root pfn_list; /* Ex-user pinned pfn list */ unsigned long *bitmap; + struct mm_struct *mm; }; struct vfio_batch { @@ -420,8 +421,8 @@ static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async) if (!npage) return 0; - mm = async ? get_task_mm(dma->task) : dma->task->mm; - if (!mm) + mm = dma->mm; + if (async && !mmget_not_zero(mm)) return -ESRCH; /* process exited */ ret = mmap_write_lock_killable(mm); @@ -794,8 +795,8 @@ static int vfio_pin_page_external(struct vfio_dma *dma, unsigned long vaddr, struct mm_struct *mm; int ret; - mm = get_task_mm(dma->task); - if (!mm) + mm = dma->mm; + if (!mmget_not_zero(mm)) return -ENODEV; ret = vaddr_get_pfns(mm, vaddr, 1, dma->prot, pfn_base, pages); @@ -805,7 +806,7 @@ static int vfio_pin_page_external(struct vfio_dma *dma, unsigned long vaddr, ret = 0; if (do_accounting && !is_invalid_reserved_pfn(*pfn_base)) { - ret = vfio_lock_acct(dma, 1, true); + ret = vfio_lock_acct(dma, 1, false); if (ret) { put_pfn(*pfn_base, dma->prot); if (ret == -ENOMEM) @@ -1180,6 +1181,7 @@ static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma) vfio_unmap_unpin(iommu, dma, true); vfio_unlink_dma(iommu, dma); put_task_struct(dma->task); + mmdrop(dma->mm); vfio_dma_bitmap_free(dma); if (dma->vaddr_invalid) { iommu->vaddr_invalid_count--; @@ -1664,29 +1666,15 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu, * against the locked memory limit and we need to be able to do both * outside of this call path as pinning can be asynchronous via the * external interfaces for mdev devices. RLIMIT_MEMLOCK requires a - * task_struct and VM locked pages requires an mm_struct, however - * holding an indefinite mm reference is not recommended, therefore we - * only hold a reference to a task. We could hold a reference to - * current, however QEMU uses this call path through vCPU threads, - * which can be killed resulting in a NULL mm and failure in the unmap - * path when called via a different thread. Avoid this problem by - * using the group_leader as threads within the same group require - * both CLONE_THREAD and CLONE_VM and will therefore use the same - * mm_struct. - * - * Previously we also used the task for testing CAP_IPC_LOCK at the - * time of pinning and accounting, however has_capability() makes use - * of real_cred, a copy-on-write field, so we can't guarantee that it - * matches group_leader, or in fact that it might not change by the - * time it's evaluated. If a process were to call MAP_DMA with - * CAP_IPC_LOCK but later drop it, it doesn't make sense that they - * possibly see different results for an iommu_mapped vfio_dma vs - * externally mapped. Therefore track CAP_IPC_LOCK in vfio_dma at the - * time of calling MAP_DMA. + * task_struct. Save the group_leader so that all DMA tracking uses + * the same task, to make debugging easier. VM locked pages requires + * an mm_struct, so grab the mm in case the task dies. */ get_task_struct(current->group_leader); dma->task = current->group_leader; dma->lock_cap = capable(CAP_IPC_LOCK); + dma->mm = current->mm; + mmgrab(dma->mm); dma->pfn_list = RB_ROOT; @@ -3131,9 +3119,8 @@ static int vfio_iommu_type1_dma_rw_chunk(struct vfio_iommu *iommu, !(dma->prot & IOMMU_READ)) return -EPERM; - mm = get_task_mm(dma->task); - - if (!mm) + mm = dma->mm; + if (!mmget_not_zero(mm)) return -EPERM; if (kthread)