linux-kernel - [RFC v2 2/4] hisi_acc_vfio_pci: Override ioctl method to limit BAR2 region size

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Date:   Fri, 2 Jul 2021 10:58:47 +0100
From:   Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
To:     <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-crypto@...r.kernel.org>
CC:     <alex.williamson@...hat.com>, <jgg@...dia.com>,
        <mgurtovoy@...dia.com>, <linuxarm@...wei.com>,
        <liulongfang@...wei.com>, <prime.zeng@...ilicon.com>,
        <yuzenghui@...wei.com>, <jonathan.cameron@...wei.com>,
        <wangzhou1@...ilicon.com>
Subject: [RFC v2 2/4] hisi_acc_vfio_pci: Override ioctl method to limit BAR2 region size

HiSilicon ACC VF device BAR2 region consists of both functional register
space and migration control register space. From a security point of
view, it's not advisable to export the migration control region to Guest.

Hence, hide the migration region and report only the functional register
space.

Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
---
 drivers/vfio/pci/hisi_acc_vfio_pci.c | 42 +++++++++++++++++++++++++++-
 1 file changed, 41 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/pci/hisi_acc_vfio_pci.c b/drivers/vfio/pci/hisi_acc_vfio_pci.c
index a9e173098ab5..d57cf6d7adaf 100644
--- a/drivers/vfio/pci/hisi_acc_vfio_pci.c
+++ b/drivers/vfio/pci/hisi_acc_vfio_pci.c
@@ -12,6 +12,46 @@
 #include <linux/vfio.h>
 #include <linux/vfio_pci_core.h>
 
+static long hisi_acc_vfio_pci_ioctl(struct vfio_device *core_vdev, unsigned int cmd,
+				    unsigned long arg)
+{
+	struct vfio_pci_core_device *vdev =
+		container_of(core_vdev, struct vfio_pci_core_device, vdev);
+
+	if (cmd == VFIO_DEVICE_GET_REGION_INFO) {
+		struct pci_dev *pdev = vdev->pdev;
+		struct vfio_region_info info;
+		unsigned long minsz;
+
+		minsz = offsetofend(struct vfio_region_info, offset);
+
+		if (copy_from_user(&info, (void __user *)arg, minsz))
+			return -EFAULT;
+
+		if (info.argsz < minsz)
+			return -EINVAL;
+
+		if (info.index == VFIO_PCI_BAR2_REGION_INDEX) {
+			info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
+
+			/*
+			 * ACC VF dev BAR2 region(64K) consists of both functional
+			 * register space and migration control register space.
+			 * Report only the first 32K(functional region) to Guest.
+			 */
+			info.size = pci_resource_len(pdev, info.index) / 2;
+
+			info.flags = VFIO_REGION_INFO_FLAG_READ |
+					VFIO_REGION_INFO_FLAG_WRITE |
+					VFIO_REGION_INFO_FLAG_MMAP;
+
+			return copy_to_user((void __user *)arg, &info, minsz) ?
+					    -EFAULT : 0;
+		}
+	}
+	return vfio_pci_core_ioctl(core_vdev, cmd, arg);
+}
+
 static int hisi_acc_vfio_pci_open(struct vfio_device *core_vdev)
 {
 	struct vfio_pci_core_device *vdev =
@@ -33,7 +73,7 @@ static const struct vfio_device_ops hisi_acc_vfio_pci_ops = {
 	.name		= "hisi-acc-vfio-pci",
 	.open		= hisi_acc_vfio_pci_open,
 	.release	= vfio_pci_core_release,
-	.ioctl		= vfio_pci_core_ioctl,
+	.ioctl		= hisi_acc_vfio_pci_ioctl,
 	.read		= vfio_pci_core_read,
 	.write		= vfio_pci_core_write,
 	.mmap		= vfio_pci_core_mmap,
-- 
2.17.1