KVM: Device assignment permission checks
[linux-2.6.git] / virt / kvm / assigned-dev.c
index a251a28..758e3b3 100644 (file)
@@ -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 +482,73 @@ 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;
@@ -516,6 +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;