s390/iucv: Fix vargs handling in iucv_alloc_device()

iucv_alloc_device() gets a format string and a varying number of
arguments. This is incorrectly forwarded by calling dev_set_name() with
the format string and a va_list, while dev_set_name() expects also a
varying number of arguments.

Symptoms:
Corrupted iucv device names, which can result in log messages like:
sysfs: cannot create duplicate filename '/devices/iucv/hvc_iucv1827699952'

Fixes: 4452e8e ("s390/iucv: Provide iucv_alloc_device() / iucv_release_device()")
Link: https://bugzilla.suse.com/show_bug.cgi?id=1228425
Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
Reviewed-by: Thorsten Winkler <twinkler@linux.ibm.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Link: https://patch.msgid.link/20240821091337.3627068-1-wintera@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: SandyWinter

net/iucv/iucv.c

@@ -86,13 +86,15 @@ struct device *iucv_alloc_device(const struct attribute_group **attrs,
 {
 	struct device *dev;
 	va_list vargs;
+	char buf[20];
 	int rc;
 
 	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 	if (!dev)
 		goto out_error;
 	va_start(vargs, fmt);
-	rc = dev_set_name(dev, fmt, vargs);
+	vsnprintf(buf, sizeof(buf), fmt, vargs);
+	rc = dev_set_name(dev, "%s", buf);
 	va_end(vargs);
 	if (rc)
 		goto out_error;