drivers/hid: fix for the big hid report length via hid_report_len()

syzbot found WARNING in hid_alloc_report_buf[1] when the raw buffer for
report is kmalloc() allocated with length > KMALLOC_MAX_SIZE, causing
order >= MAX_ORDER condition.

u8 *hid_alloc_report_buf(struct hid_report *report, gfp_t flags)
{
	u32 len = hid_report_len(report) + 7;

	return kmalloc(len, flags);
}

The restriction with HID_MAX_BUFFER_SIZE (16kb) is, seems, a valid max
limit. I've come up with this in all hid_report_len() xrefs.

The fix inside hid_report_len(), not in *hid_alloc_report_buf() is also
fixing out-of-bounds here in memcpy():

statc int hid_submit_ctrl()
{
..
	len = hid_report_len(report);
	if (dir == USB_DIR_OUT) {
		..
		if (raw_report) {
			memcpy(usbhid->ctrlbuf, raw_report, len);
..

So I've decided to return HID_MAX_BUFFER_SIZE if it the report length is
bigger than limit, otherwise the return the report length.

[1]
Call Trace:
 alloc_pages include/linux/gfp.h:547 [inline]
 kmalloc_order+0x40/0x130 mm/slab_common.c:837
 kmalloc_order_trace+0x15/0x70 mm/slab_common.c:853
 kmalloc_large include/linux/slab.h:481 [inline]
 __kmalloc+0x257/0x330 mm/slub.c:3974
 kmalloc include/linux/slab.h:557 [inline]
 hid_alloc_report_buf+0x70/0xa0 drivers/hid/hid-core.c:1648
 __usbhid_submit_report drivers/hid/usbhid/hid-core.c:590 [inline]

Reported-by: syzbot+ab02336a647181a886a6@syzkaller.appspotmail.com
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
Change-Id: I99cfadb6d873b7c3f8354036804d7e8395059d60
diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c
index 86257ce..4e90773 100644
--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c
@@ -374,7 +374,7 @@
 	raw_report = usbhid->ctrl[usbhid->ctrltail].raw_report;
 	dir = usbhid->ctrl[usbhid->ctrltail].dir;
 
-	len = ((report->size - 1) >> 3) + 1 + (report->id > 0);
+	len = hid_report_len(report);
 	if (dir == USB_DIR_OUT) {
 		usbhid->urbctrl->pipe = usb_sndctrlpipe(hid_to_usb_dev(hid), 0);
 		usbhid->urbctrl->transfer_buffer_length = len;
diff --git a/include/linux/hid.h b/include/linux/hid.h
index c39d71e..682ec11 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -1156,7 +1156,8 @@
 static inline u32 hid_report_len(struct hid_report *report)
 {
 	/* equivalent to DIV_ROUND_UP(report->size, 8) + !!(report->id > 0) */
-	return ((report->size - 1) >> 3) + 1 + (report->id > 0);
+	u32 len = ((report->size - 1) >> 3) + 1 + (report->id > 0);
+	return len > HID_MAX_BUFFER_SIZE ? HID_MAX_BUFFER_SIZE : len;
 }
 
 int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, u32 size,