media: gspca: zero usb_buf

Allocate gspca_dev->usb_buf with kzalloc instead of kmalloc to
ensure it is property zeroed. This fixes various syzbot errors
about uninitialized data.

Syzbot links:

https://syzkaller.appspot.com/bug?extid=32310fc2aea76898d074
https://syzkaller.appspot.com/bug?extid=99706d6390be1ac542a2
https://syzkaller.appspot.com/bug?extid=64437af5c781a7f0e08e

Reported-and-tested-by: [e-mail]
Reported-and-tested-by: [e-mail]
Reported-and-tested-by: [e-mail]

Signed-off-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/usb/gspca/gspca.c

···
 		pr_err("couldn't kzalloc gspca struct\n");
 		return -ENOMEM;
 	}
-	gspca_dev->usb_buf = kmalloc(USB_BUF_SZ, GFP_KERNEL);
+	gspca_dev->usb_buf = kzalloc(USB_BUF_SZ, GFP_KERNEL);
 	if (!gspca_dev->usb_buf) {
 		pr_err("out of memory\n");
 		ret = -ENOMEM;