[PATCH 5.10 08/19] HID: core: Fix deadloop in hid_apply_multiplier.

Greg Kroah-Hartman
2023-03-01T18:09:56Z

From: Xin Zhao <xnzhao@google.com>

[ 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: Xin Zhao <xnzhao@google.com>
Link: https://lore.kernel.org/r/20230130212947.1315941-1-xnzhao@google.com
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/hid/hid-core.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index baadead947c8b..5f9ec1d1464a2 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -1197,6 +1197,7 @@ 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,
@@ -1247,6 +1248,8 @@ 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) {
--
2.39.0