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HID: core: fix number/pointer type confusion on long items

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When fetch_item() is called by hid_scan_report() on an item with
HID_ITEM_TAG_LONG, it stores a pointer to the item data in
item->data.longdata instead of storing a value directly in
item->data.{u8/u16/u32}.

When item_udata() or item_sdata() encounters such an item, it incorrectly
assumes that the item is in short format, and therefore returns the lower
part of a kernel pointer reinterpreted as a number.

When a HID device is connected whose descriptor contains a
HID_GLOBAL_ITEM_TAG_REPORT_SIZE encoded in long format with size=4, this
causes the lower half of a kernel pointer to be printed into dmesg as a
number, like this:

    hid (null): invalid report_size 107953555

To fix it, let item_udata() and item_sdata() verify that the item is in
short format.

Note that this bug only affects hid_scan_report(), while the main parsing
pass hid_parse_collections() will always bail out when encountering a long
item.

Sidenote: There are currently no users of data.longdata; maybe we should
just remove any parsing of long-format descriptors as a follow-up.

Fixes: 3dc8fc083d ("HID: Use hid_parser for pre-scanning the report descriptors")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>
This commit is contained in:
Jann Horn
2026-07-03 20:30:02 +02:00
committed by Jiri Kosina
parent b57af24482
commit 28abce9513
1 changed files with 6 additions and 0 deletions
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6
drivers/hid/hid-core.c
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@@ -379,6 +379,9 @@ static int hid_add_field(struct hid_parser *parser, unsigned report_type, unsign
static u32 item_udata(struct hid_item *item)
{
if (item->format != HID_ITEM_FORMAT_SHORT)
return 0;
switch (item->size) {
case 1: return item->data.u8;
case 2: return item->data.u16;
@@ -389,6 +392,9 @@ static u32 item_udata(struct hid_item *item)
static s32 item_sdata(struct hid_item *item)
{
if (item->format != HID_ITEM_FORMAT_SHORT)
return 0;
switch (item->size) {
case 1: return item->data.s8;
case 2: return item->data.s16;