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Commit 23affaed authored by Xin Zhao's avatar Xin Zhao Committed by Greg Kroah-Hartman
Browse files

HID: core: Fix deadloop in hid_apply_multiplier. 



[ Upstream commit ea427a222d8bdf2bc1a8a6da3ebe247f7dced70c ]

The initial value of hid->collection[].parent_idx if 0. When
Report descriptor doesn't contain "HID Collection", the value
remains as 0.

In the meanwhile, when the Report descriptor fullfill
all following conditions, it will trigger hid_apply_multiplier
function call.
1. Usage page is Generic Desktop Ctrls (0x01)
2. Usage is RESOLUTION_MULTIPLIER (0x48)
3. Contain any FEATURE items

The while loop in hid_apply_multiplier will search the top-most
collection by searching parent_idx == -1. Because all parent_idx
is 0. The loop will run forever.

There is a Report Descriptor triggerring the deadloop
0x05, 0x01,        // Usage Page (Generic Desktop Ctrls)
0x09, 0x48,        // Usage (0x48)
0x95, 0x01,        // Report Count (1)
0x75, 0x08,        // Report Size (8)
0xB1, 0x01,        // Feature

Signed-off-by: default avatarXin Zhao <xnzhao@google.com>
Link: https://lore.kernel.org/r/20230130212947.1315941-1-xnzhao@google.com


Signed-off-by: default avatarBenjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 93b17c7e

drivers/hid/hid-core.c

+3 −0
Original line number Diff line number Diff line
@@ -1190,6 +1190,7 @@ int hid_open_report(struct hid_device *device) 
	__u8 *end;

	__u8 *next;

	int ret;

	int i;

	static int (*dispatch_type[])(struct hid_parser *parser,

				      struct hid_item *item) = {

		hid_parser_main,
@@ -1240,6 +1241,8 @@ int hid_open_report(struct hid_device *device) 
		goto err;

	}

	device->collection_size = HID_DEFAULT_NUM_COLLECTIONS;

	for (i = 0; i < HID_DEFAULT_NUM_COLLECTIONS; i++)

		device->collection[i].parent_idx = -1;



	ret = -EINVAL;

	while ((next = fetch_item(start, end, &item)) != NULL) {