usb: gadget: f_fs: check for allocation failure

Return -ENOMEM if kmalloc() fails.

Fixes: 9353afbbfa7b ('usb: gadget: f_fs: buffer data from ‘oversized’ OUT requests')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/function/f_fs.c

@@ -775,6 +775,8 @@ static ssize_t __ffs_epfile_read_data(struct ffs_epfile *epfile,
 
 	data_len -= ret;
 	buf = kmalloc(sizeof(*buf) + data_len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
 	buf->length = data_len;
 	buf->data = buf->storage;
 	memcpy(buf->storage, data + ret, data_len);