[PATCH] udevProcessCSS: fix segfault

[Marc Hartmayer]

Don't process subchannel devices where `def->driver` is not set. This
fixes the following segfault:

Thread 21 "nodedev-init" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x3ffb08fc910 (LWP 64303)]
(gdb) bt
 #0  0x000003fffd1272b4 in __strcmp_vx () at /lib64/libc.so.6
 #1  0x000003ffc260c3a8 in udevProcessCSS (device=0x3ff9018d130, def=0x3ff90194a90)
 #2  0x000003ffc260cb78 in udevGetDeviceDetails (device=0x3ff9018d130, def=0x3ff90194a90)
 #3  0x000003ffc260d126 in udevAddOneDevice (device=0x3ff9018d130)
 #4  0x000003ffc260d414 in udevProcessDeviceListEntry (udev=0x3ffa810d800, list_entry=0x3ff90001990)
 #5  0x000003ffc260d638 in udevEnumerateDevices (udev=0x3ffa810d800)
 #6  0x000003ffc260e08e in nodeStateInitializeEnumerate (opaque=0x3ffa810d800)
 #7  0x000003fffdaa14b6 in virThreadHelper (data=0x3ffa810df00)
 #8  0x000003fffc309ed6 in start_thread ()
 #9  0x000003fffd185e66 in thread_start ()
(gdb) p *def
$2 = {
  name = 0x0,
  sysfs_path = 0x3ff90198e80 "/sys/devices/css0/0.0.ff40",
  parent = 0x0,
  parent_sysfs_path = 0x0,
  parent_wwnn = 0x0,
  parent_wwpn = 0x0,
  parent_fabric_wwn = 0x0,
  driver = 0x0,
  devnode = 0x0,
  devlinks = 0x3ff90194670,
  caps = 0x3ff90194380
}

Fixes: 05e6cdafa6e0 ("node_device: detect CSS devices")
Reviewed-by: Boris Fiuczynski <fiuczy at linux.ibm.com>
Signed-off-by: Marc Hartmayer <mhartmay at linux.ibm.com>
---
 src/node_device/node_device_udev.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c
index 5f2841bb7d8e..12e3f30badd1 100644
--- a/src/node_device/node_device_udev.c
+++ b/src/node_device/node_device_udev.c
@@ -1130,8 +1130,9 @@ udevProcessCSS(struct udev_device *device,
                virNodeDeviceDefPtr def)
 {
     /* only process IO subchannel and vfio-ccw devices to keep the list sane */
-    if (STRNEQ(def->driver, "io_subchannel") &&
-        STRNEQ(def->driver, "vfio_ccw"))
+    if (!def->driver ||
+        (STRNEQ(def->driver, "io_subchannel") &&
+         STRNEQ(def->driver, "vfio_ccw")))
         return -1;
 
     if (udevGetCCWAddress(def->sysfs_path, &def->caps->data) < 0)
-- 
2.25.4