1 files changed, 84 insertions, 9 deletions

diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
index 3ad0925d23a9..758e3b36d4cf 100644
--- a/virt/kvm/assigned-dev.c
+++ b/virt/kvm/assigned-dev.c
@@ -17,6 +17,8 @@
 #include <linux/pci.h>
 #include <linux/interrupt.h>
 #include <linux/slab.h>
+#include <linux/namei.h>
+#include <linux/fs.h>
 #include "irq.h"
 
 static struct kvm_assigned_dev_kernel *kvm_find_assigned_dev(struct list_head *head,
@@ -480,12 +482,76 @@ out:
         return r;
 }
 
+/*
+ * We want to test whether the caller has been granted permissions to
+ * use this device.  To be able to configure and control the device,
+ * the user needs access to PCI configuration space and BAR resources.
+ * These are accessed through PCI sysfs.  PCI config space is often
+ * passed to the process calling this ioctl via file descriptor, so we
+ * can't rely on access to that file.  We can check for permissions
+ * on each of the BAR resource files, which is a pretty clear
+ * indicator that the user has been granted access to the device.
+ */
+static int probe_sysfs_permissions(struct pci_dev *dev)
+{
+#ifdef CONFIG_SYSFS
+        int i;
+        bool bar_found = false;
+
+        for (i = PCI_STD_RESOURCES; i <= PCI_STD_RESOURCE_END; i++) {
+                char *kpath, *syspath;
+                struct path path;
+                struct inode *inode;
+                int r;
+
+                if (!pci_resource_len(dev, i))
+                        continue;
+
+                kpath = kobject_get_path(&dev->dev.kobj, GFP_KERNEL);
+                if (!kpath)
+                        return -ENOMEM;
+
+                /* Per sysfs-rules, sysfs is always at /sys */
+                syspath = kasprintf(GFP_KERNEL, "/sys%s/resource%d", kpath, i);
+                kfree(kpath);
+                if (!syspath)
+                        return -ENOMEM;
+
+                r = kern_path(syspath, LOOKUP_FOLLOW, &path);
+                kfree(syspath);
+                if (r)
+                        return r;
+
+                inode = path.dentry->d_inode;
+
+                r = inode_permission(inode, MAY_READ | MAY_WRITE | MAY_ACCESS);
+                path_put(&path);
+                if (r)
+                        return r;
+
+                bar_found = true;
+        }
+
+        /* If no resources, probably something special */
+        if (!bar_found)
+                return -EPERM;
+
+        return 0;
+#else
+        return -EINVAL; /* No way to control the device without sysfs */
+#endif
+}
+
 static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
                                       struct kvm_assigned_pci_dev *assigned_dev)
 {
         int r = 0, idx;
         struct kvm_assigned_dev_kernel *match;
         struct pci_dev *dev;
+        u8 header_type;
+
+        if (!(assigned_dev->flags & KVM_DEV_ASSIGN_ENABLE_IOMMU))
+                return -EINVAL;
 
         mutex_lock(&kvm->lock);
         idx = srcu_read_lock(&kvm->srcu);
@@ -513,6 +579,18 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
                 r = -EINVAL;
                 goto out_free;
         }
+
+        /* Don't allow bridges to be assigned */
+        pci_read_config_byte(dev, PCI_HEADER_TYPE, &header_type);
+        if ((header_type & PCI_HEADER_TYPE) != PCI_HEADER_TYPE_NORMAL) {
+                r = -EPERM;
+                goto out_put;
+        }
+
+        r = probe_sysfs_permissions(dev);
+        if (r)
+                goto out_put;
+
         if (pci_enable_device(dev)) {
                 printk(KERN_INFO "%s: Could not enable PCI device\n", __func__);
                 r = -EBUSY;
@@ -544,16 +622,14 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
 
         list_add(&match->list, &kvm->arch.assigned_dev_head);
 
-        if (assigned_dev->flags & KVM_DEV_ASSIGN_ENABLE_IOMMU) {
-                if (!kvm->arch.iommu_domain) {
-                        r = kvm_iommu_map_guest(kvm);
-                        if (r)
-                                goto out_list_del;
-                }
-                r = kvm_assign_device(kvm, match);
+        if (!kvm->arch.iommu_domain) {
+                r = kvm_iommu_map_guest(kvm);
                 if (r)
                         goto out_list_del;
         }
+        r = kvm_assign_device(kvm, match);
+        if (r)
+                goto out_list_del;
 
 out:
         srcu_read_unlock(&kvm->srcu, idx);
@@ -593,8 +669,7 @@ static int kvm_vm_ioctl_deassign_device(struct kvm *kvm,
                 goto out;
         }
 
-        if (match->flags & KVM_DEV_ASSIGN_ENABLE_IOMMU)
-                kvm_deassign_device(kvm, match);
+        kvm_deassign_device(kvm, match);
 
         kvm_free_assigned_device(kvm, match);