[PATCH -next] iio: buffer: Check the return value of kstrdup_const()

[Wang Wensheng <wangwensheng4@huawei.com>]

We should check the duplication of attr.name properly in
iio_buffer_wrap_attr() or a null-pointer-dereference would
occur on destroying the related sysfs file.
This issue is found by fault-injection.

BUG: kernel NULL pointer dereference, address: 0000000000000000
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
RIP: 0010:strlen+0x0/0x20
Call Trace:
 kernfs_name_hash+0x1c/0xb0
 kernfs_find_ns+0xc6/0x160
 kernfs_remove_by_name_ns+0x5c/0xb0
 remove_files.isra.1+0x42/0x90
 internal_create_group+0x42f/0x460
 internal_create_groups+0x49/0xc0
 device_add+0xb5b/0xbe0
 ? kobject_get+0x90/0xa0
 cdev_device_add+0x2b/0x90
 __iio_device_register+0xa56/0xb40

Fixes: 15097c7a1adc ("iio: buffer: wrap all buffer attributes into iio_dev_attr")
Reported-by: Hulk Robot<hulkci@huawei.com>
Signed-off-by: Wang Wensheng <wangwensheng4@huawei.com>
---
 drivers/iio/industrialio-buffer.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index c648e9553edd..f4011c477bac 100644
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -1312,6 +1312,8 @@ static struct attribute *iio_buffer_wrap_attr(struct iio_buffer *buffer,
 	iio_attr->buffer = buffer;
 	memcpy(&iio_attr->dev_attr, dattr, sizeof(iio_attr->dev_attr));
 	iio_attr->dev_attr.attr.name = kstrdup_const(attr->name, GFP_KERNEL);
+	if (!iio_attr->dev_attr.attr.name)
+		return NULL;
 	sysfs_attr_init(&iio_attr->dev_attr.attr);
 
 	list_add(&iio_attr->l, &buffer->buffer_attr_list);
-- 
2.17.1