iio: trigger: sysfs: fix possible memory leak in iio_sysfs_trig_init()

dev_set_name() allocates memory for name, it need be freed
when device_add() fails, call put_device() to give up the
reference that hold in device_initialize(), so that it can
be freed in kobject_cleanup() when the refcount hit to 0.

Fault injection test can trigger this:

unreferenced object 0xffff8e8340a7b4c0 (size 32):
  comm "modprobe", pid 243, jiffies 4294678145 (age 48.845s)
  hex dump (first 32 bytes):
    69 69 6f 5f 73 79 73 66 73 5f 74 72 69 67 67 65  iio_sysfs_trigge
    72 00 a7 40 83 8e ff ff 00 86 13 c4 f6 ee ff ff  r..@............
  backtrace:
    [<0000000074999de8>] __kmem_cache_alloc_node+0x1e9/0x360
    [<00000000497fd30b>] __kmalloc_node_track_caller+0x44/0x1a0
    [<000000003636c520>] kstrdup+0x2d/0x60
    [<0000000032f84da2>] kobject_set_name_vargs+0x1e/0x90
    [<0000000092efe493>] dev_set_name+0x4e/0x70

Fixes: 1f78568 ("staging:iio:trigger sysfs userspace trigger rework.")
Signed-off-by: Yang Yingliang <[email protected]>
Cc: <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jonathan Cameron <[email protected]>

Author: Yang Yingliang

drivers/iio/trigger/iio-trig-sysfs.c

@@ -203,9 +203,13 @@ static int iio_sysfs_trigger_remove(int id)
 
 static int __init iio_sysfs_trig_init(void)
 {
+	int ret;
 	device_initialize(&iio_sysfs_trig_dev);
 	dev_set_name(&iio_sysfs_trig_dev, "iio_sysfs_trigger");
-	return device_add(&iio_sysfs_trig_dev);
+	ret = device_add(&iio_sysfs_trig_dev);
+	if (ret)
+		put_device(&iio_sysfs_trig_dev);
+	return ret;
 }
 module_init(iio_sysfs_trig_init);