[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: [libvirt] [PATCH 5/7] qemuDomainGetHostdevPath: Create /dev/vfio/vfio iff needed



Hi

On Fri, Feb 10, 2017 at 6:57 PM Michal Privoznik <mprivozn redhat com> wrote:
So far, we are allowing /dev/vfio/vfio in the devices cgroup
unconditionally (and creating it in the namespace too). Even if
domain has no hostdev assignment configured. This is potential
security hole. Therefore, when starting the domain (or
hotplugging a hostdev) create & allow /dev/vfio/vfio too (if
needed).

Signed-off-by: Michal Privoznik <mprivozn redhat com>

looks good to me,


Reviewed-by: Marc-André Lureau <marcandre lureau redhat com>

 
---
 src/qemu/qemu.conf                 |   2 +-
 src/qemu/qemu_cgroup.c             |  53 ++++++++++++----
 src/qemu/qemu_domain.c             | 124 ++++++++++++++++++++++++-------------
 src/qemu/qemu_domain.h             |   5 +-
 src/qemu/test_libvirtd_qemu.aug.in |   1 -
 5 files changed, 125 insertions(+), 60 deletions(-)

diff --git a/src/qemu/qemu.conf b/src/qemu/qemu.conf
index 97d769d42..9f990c20d 100644
--- a/src/qemu/qemu.conf
+++ b/src/qemu/qemu.conf
@@ -354,7 +354,7 @@
 #    "/dev/null", "/dev/full", "/dev/zero",
 #    "/dev/random", "/dev/urandom",
 #    "/dev/ptmx", "/dev/kvm", "/dev/kqemu",
-#    "/dev/rtc","/dev/hpet", "/dev/vfio/vfio"
+#    "/dev/rtc","/dev/hpet"
 #]
 #
 # RDMA migration requires the following extra files to be added to the list:
diff --git a/src/qemu/qemu_cgroup.c b/src/qemu/qemu_cgroup.c
index 19832c209..944e8dc87 100644
--- a/src/qemu/qemu_cgroup.c
+++ b/src/qemu/qemu_cgroup.c
@@ -46,12 +46,13 @@ const char *const defaultDeviceACL[] = {
     "/dev/null", "/dev/full", "/dev/zero",
     "/dev/random", "/dev/urandom",
     "/dev/ptmx", "/dev/kvm", "/dev/kqemu",
-    "/dev/rtc", "/dev/hpet", "/dev/vfio/vfio",
+    "/dev/rtc", "/dev/hpet",
     NULL,
 };
 #define DEVICE_PTY_MAJOR 136
 #define DEVICE_SND_MAJOR 116

+#define DEV_VFIO "/dev/vfio/vfio"

 static int
 qemuSetupImagePathCgroup(virDomainObjPtr vm,
@@ -265,26 +266,31 @@ qemuSetupHostdevCgroup(virDomainObjPtr vm,
                        virDomainHostdevDefPtr dev)
 {
     qemuDomainObjPrivatePtr priv = vm->privateData;
-    char *path = NULL;
-    int perms;
-    int ret = -1;
+    char **path = NULL;
+    int *perms = NULL;
+    size_t i, npaths = 0;
+    int rv, ret = -1;

-    if (qemuDomainGetHostdevPath(dev, &path, &perms) < 0)
+    if (qemuDomainGetHostdevPath(dev, &npaths, &path, &perms) < 0)
         goto cleanup;

-    if (!path) {
-        /* There's no path that we need to allow. Claim success. */
-        ret = 0;
-        goto cleanup;
+    for (i = 0; i < npaths; i++) {
+        VIR_DEBUG("Cgroup allow %s perms=%d", path[i], perms[i]);
+        rv = virCgroupAllowDevicePath(priv->cgroup, path[i], perms[i], false);
+        virDomainAuditCgroupPath(vm, priv->cgroup, "allow", path[i],
+                                 virCgroupGetDevicePermsString(perms[i]),
+                                 ret == 0);
+        if (rv < 0)
+            goto cleanup;
     }

-    VIR_DEBUG("Cgroup allow %s perms=%d", path, perms);
-    ret = virCgroupAllowDevicePath(priv->cgroup, path, perms, false);
-    virDomainAuditCgroupPath(vm, priv->cgroup, "allow", path,
-                             virCgroupGetDevicePermsString(perms), ret == 0);
+    ret = 0;

  cleanup:
+    for (i = 0; i < npaths; i++)
+        VIR_FREE(path[i]);
     VIR_FREE(path);
+    VIR_FREE(perms);
     return ret;
 }

@@ -312,6 +318,7 @@ qemuTeardownHostdevCgroup(virDomainObjPtr vm,
         case VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_PCI:
             if (pcisrc->backend == VIR_DOMAIN_HOSTDEV_PCI_BACKEND_VFIO) {
                 int rv;
+                size_t i, vfios = 0;

                 pci = virPCIDeviceNew(pcisrc->addr.domain,
                                       pcisrc->addr.bus,
@@ -330,6 +337,26 @@ qemuTeardownHostdevCgroup(virDomainObjPtr vm,
                                          "deny", path, "rwm", rv == 0);
                 if (rv < 0)
                     goto cleanup;
+
+                /* If this is the last hostdev with VFIO backend deny
+                 * /dev/vfio/vfio too. */
+                for (i = 0; i < vm->def->nhostdevs; i++) {
+                    virDomainHostdevDefPtr tmp = vm->def->hostdevs[i];
+                    if (tmp->mode == VIR_DOMAIN_HOSTDEV_MODE_SUBSYS &&
+                        tmp->source.subsys.type == VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_PCI &&
+                        tmp->source.subsys.u.pci.backend == VIR_DOMAIN_HOSTDEV_PCI_BACKEND_VFIO)
+                        vfios++;
+                }
+
+                if (vfios == 0) {
+                    VIR_DEBUG("Cgroup deny " DEV_VFIO " for PCI device assignment");
+                    rv = virCgroupDenyDevicePath(priv->cgroup, DEV_VFIO,
+                                                 VIR_CGROUP_DEVICE_RWM, false);
+                    virDomainAuditCgroupPath(vm, priv->cgroup,
+                                             "deny", DEV_VFIO, "rwm", rv == 0);
+                    if (rv < 0)
+                        goto cleanup;
+                }
             }
             break;
         case VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_USB:
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index c6d32525f..530eced33 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -107,6 +107,7 @@ VIR_ENUM_IMPL(qemuDomainNamespace, QEMU_DOMAIN_NS_LAST,

 #define PROC_MOUNTS "/proc/mounts"
 #define DEVPREFIX "/dev/"
+#define DEV_VFIO "/dev/vfio/vfio"


 struct _qemuDomainLogContext {
@@ -6834,18 +6835,24 @@ qemuDomainSupportsVideoVga(virDomainVideoDefPtr video,
 /**
  * qemuDomainGetHostdevPath:
  * @dev: host device definition
+ * @npaths: number of items in @path and @perms arrays
  * @path: resulting path to @dev
  * @perms: Optional pointer to VIR_CGROUP_DEVICE_* perms
  *
- * For given device @dev fetch its host path and store it at @path. Optionally,
- * caller can get @perms on the path (e.g. rw/ro).
+ * For given device @dev fetch its host path and store it at
+ * @path. If a device requires other paths to be present/allowed
+ * they are stored in the @path array after the actual path.
+ * Optionally, caller can get @perms on the path (e.g. rw/ro).
+ *
+ * The caller is responsible for freeing the memory.
  *
  * Returns 0 on success, -1 otherwise.
  */
 int
 qemuDomainGetHostdevPath(virDomainHostdevDefPtr dev,
-                         char **path,
-                         int *perms)
+                         size_t *npaths,
+                         char ***path,
+                         int **perms)
 {
     int ret = -1;
     virDomainHostdevSubsysUSBPtr usbsrc = &dev->source.subsys.u.usb;
@@ -6858,8 +6865,13 @@ qemuDomainGetHostdevPath(virDomainHostdevDefPtr dev,
     virSCSIVHostDevicePtr host = NULL;
     char *tmpPath = NULL;
     bool freeTmpPath = false;
+    bool includeVFIO = false;
+    char **tmpPaths = NULL;
+    int *tmpPerms = NULL;
+    size_t i, tmpNpaths = 0;
+    int perm = 0;

-    *path = NULL;
+    *npaths = 0;

     switch ((virDomainHostdevMode) dev->mode) {
     case VIR_DOMAIN_HOSTDEV_MODE_SUBSYS:
@@ -6876,8 +6888,9 @@ qemuDomainGetHostdevPath(virDomainHostdevDefPtr dev,
                 if (!(tmpPath = virPCIDeviceGetIOMMUGroupDev(pci)))
                     goto cleanup;
                 freeTmpPath = true;
-                if (perms)
-                    *perms = VIR_CGROUP_DEVICE_RW;
+
+                perm = VIR_CGROUP_DEVICE_RW;
+                includeVFIO = true;
             }
             break;

@@ -6892,8 +6905,7 @@ qemuDomainGetHostdevPath(virDomainHostdevDefPtr dev,

             if (!(tmpPath = (char *) virUSBDeviceGetPath(usb)))
                 goto cleanup;
-            if (perms)
-                *perms = VIR_CGROUP_DEVICE_RW;
+            perm = VIR_CGROUP_DEVICE_RW;
             break;

         case VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_SCSI:
@@ -6918,9 +6930,8 @@ qemuDomainGetHostdevPath(virDomainHostdevDefPtr dev,

                 if (!(tmpPath = (char *) virSCSIDeviceGetPath(scsi)))
                     goto cleanup;
-                if (perms)
-                    *perms = virSCSIDeviceGetReadonly(scsi) ?
-                        VIR_CGROUP_DEVICE_READ :VIR_CGROUP_DEVICE_RW;
+                perm = virSCSIDeviceGetReadonly(scsi) ?
+                    VIR_CGROUP_DEVICE_READ :VIR_CGROUP_DEVICE_RW;
             }
             break;

@@ -6932,8 +6943,7 @@ qemuDomainGetHostdevPath(virDomainHostdevDefPtr dev,

                 if (!(tmpPath = (char *) virSCSIVHostDeviceGetPath(host)))
                     goto cleanup;
-                if (perms)
-                    *perms = VIR_CGROUP_DEVICE_RW;
+                perm = VIR_CGROUP_DEVICE_RW;
             }
             break;
         }
@@ -6949,11 +6959,40 @@ qemuDomainGetHostdevPath(virDomainHostdevDefPtr dev,
         break;
     }

-    if (VIR_STRDUP(*path, tmpPath) < 0)
-        goto cleanup;
+    if (tmpPath) {
+        size_t toAlloc = 1;

+        if (includeVFIO)
+            toAlloc = 2;
+
+        if (VIR_ALLOC_N(tmpPaths, toAlloc) < 0 ||
+            VIR_ALLOC_N(tmpPerms, toAlloc) < 0 ||
+            VIR_STRDUP(tmpPaths[0], tmpPath) < 0)
+            goto cleanup;
+        tmpNpaths = toAlloc;
+        tmpPerms[0] = perm;
+
+        if (includeVFIO) {
+            if (VIR_STRDUP(tmpPaths[1], DEV_VFIO) < 0)
+                goto cleanup;
+            tmpPerms[1] = VIR_CGROUP_DEVICE_RW;
+        }
+    }
+
+    *npaths = tmpNpaths;
+    tmpNpaths = 0;
+    *path = tmpPaths;
+    tmpPaths = NULL;
+    if (perms) {
+        *perms = tmpPerms;
+        tmpPerms = NULL;
+    }
     ret = 0;
  cleanup:
+    for (i = 0; i < tmpNpaths; i++)
+        VIR_FREE(tmpPaths[i]);
+    VIR_FREE(tmpPaths);
+    VIR_FREE(tmpPerms);
     virPCIDeviceFree(pci);
     virUSBDeviceFree(usb);
     virSCSIDeviceFree(scsi);
@@ -7347,22 +7386,21 @@ qemuDomainSetupHostdev(virQEMUDriverPtr driver ATTRIBUTE_UNUSED,
                        const char *devPath)
 {
     int ret = -1;
-    char *path = NULL;
+    char **path = NULL;
+    size_t i, npaths = 0;

-    if (qemuDomainGetHostdevPath(dev, &path, NULL) < 0)
+    if (qemuDomainGetHostdevPath(dev, &npaths, &path, NULL) < 0)
         goto cleanup;

-    if (!path) {
-        /* There's no /dev device that we need to create. Claim success. */
-        ret = 0;
-        goto cleanup;
+    for (i = 0; i < npaths; i++) {
+        if (qemuDomainCreateDevice(path[i], devPath, false) < 0)
+            goto cleanup;
     }

-    if (qemuDomainCreateDevice(path, devPath, false) < 0)
-        goto cleanup;
-
     ret = 0;
  cleanup:
+    for (i = 0; i < npaths; i++)
+        VIR_FREE(path[i]);
     VIR_FREE(path);
     return ret;
 }
@@ -7980,26 +8018,26 @@ qemuDomainNamespaceSetupHostdev(virQEMUDriverPtr driver,
                                 virDomainHostdevDefPtr hostdev)
 {
     int ret = -1;
-    char *path = NULL;
+    char **path = NULL;
+    size_t i, npaths = 0;

     if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT))
         return 0;

-    if (qemuDomainGetHostdevPath(hostdev, &path, NULL) < 0)
+    if (qemuDomainGetHostdevPath(hostdev, &npaths, &path, NULL) < 0)
         goto cleanup;

-    if (!path) {
-        /* There's no /dev device that we need to create. Claim success. */
-        ret = 0;
+    for (i = 0; i < npaths; i++) {
+        if (qemuDomainAttachDeviceMknod(driver,
+                                        vm,
+                                        path[i]) < 0)
         goto cleanup;
     }

-    if (qemuDomainAttachDeviceMknod(driver,
-                                    vm,
-                                    path) < 0)
-        goto cleanup;
     ret = 0;
  cleanup:
+    for (i = 0; i < npaths; i++)
+        VIR_FREE(path[i]);
     VIR_FREE(path);
     return ret;
 }
@@ -8011,25 +8049,25 @@ qemuDomainNamespaceTeardownHostdev(virQEMUDriverPtr driver,
                                    virDomainHostdevDefPtr hostdev)
 {
     int ret = -1;
-    char *path = NULL;
+    char **path = NULL;
+    size_t i, npaths = 0;

     if (!qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT))
         return 0;

-    if (qemuDomainGetHostdevPath(hostdev, &path, NULL) < 0)
+    if (qemuDomainGetHostdevPath(hostdev, &npaths, &path, NULL) < 0)
         goto cleanup;

-    if (!path) {
-        /* There's no /dev device that we need to create. Claim success. */
-        ret = 0;
-        goto cleanup;
-    }
-
-    if (qemuDomainDetachDeviceUnlink(driver, vm, path) < 0)
+    /* Don't remove other paths than for the @hostdev itself.
+     * They might be still in use by other devices. */
+    if (npaths > 0 &&
+        qemuDomainDetachDeviceUnlink(driver, vm, path[0]) < 0)
         goto cleanup;

     ret = 0;
  cleanup:
+    for (i = 0; i < npaths; i++)
+        VIR_FREE(path[i]);
     VIR_FREE(path);
     return ret;
 }
diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
index f81550e2f..e64aa25ba 100644
--- a/src/qemu/qemu_domain.h
+++ b/src/qemu/qemu_domain.h
@@ -803,8 +803,9 @@ bool qemuDomainSupportsVideoVga(virDomainVideoDefPtr video,
                                 virQEMUCapsPtr qemuCaps);

 int qemuDomainGetHostdevPath(virDomainHostdevDefPtr dev,
-                             char **path,
-                             int *perms);
+                             size_t *npaths,
+                             char ***path,
+                             int **perms);

 int qemuDomainBuildNamespace(virQEMUDriverPtr driver,
                              virDomainObjPtr vm);
diff --git a/src/qemu/test_libvirtd_qemu.aug.in b/src/qemu/test_libvirtd_qemu.aug.in
index bd25235d3..6f03898c0 100644
--- a/src/qemu/test_libvirtd_qemu.aug.in
+++ b/src/qemu/test_libvirtd_qemu.aug.in
@@ -55,7 +55,6 @@ module Test_libvirtd_qemu =
     { "8" = "/dev/kqemu" }
     { "9" = "/dev/rtc" }
     { "10" = "/dev/hpet" }
-    { "11" = "/dev/vfio/vfio" }
 }
 { "save_image_format" = "raw" }
 { "dump_image_format" = "raw" }
--
2.11.0

--
libvir-list mailing list
libvir-list redhat com
https://www.redhat.com/mailman/listinfo/libvir-list
--
Marc-André Lureau

[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]