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HID: core: quiesce input in hid_hw_stop() to prevent use-after-free

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A driver's probe calls hid_device_io_start() to enable input delivery,
then fails at a later initialization step and unwinds via hid_hw_stop().
The unwind frees struct hidraw via hidraw_disconnect() while in-flight
HID reports may still be running on another CPU, dereferencing the
freed object through hidraw_report_event(). syzbot reports the
resulting use-after-free for the corsair-psu HID driver.

Edward Adam Davis posted a per-driver fix for corsair-psu that adds
an explicit hid_device_io_stop() before hid_hw_stop() in the probe
error path ("hwmon: prevent packets from going to driver for probe",
2026-04-28). Auditing the tree shows 15 drivers call
hid_device_io_start(); 7 also call hid_device_io_stop() and 8 do not:

  drivers calling hid_device_io_start() without a matching
  hid_device_io_stop() before hid_hw_stop():
    drivers/hwmon/corsair-psu.c       (fix posted by Edward)
    drivers/hwmon/corsair-cpro.c
    drivers/hwmon/nzxt-kraken3.c
    drivers/hwmon/nzxt-smart2.c
    drivers/hwmon/gigabyte_waterforce.c
    drivers/hid/hid-logitech-dj.c
    drivers/hid/hid-nintendo.c
    drivers/hid/hid-mcp2221.c

Roughly half of all callers of the API are exposed. Centralize the
quiesce in hid_hw_stop() so callers do not have to remember the
matching stop: if a driver has left hdev->io_started true on entry,
call hid_device_io_stop() before hid_disconnect().

For the 7 drivers that already call hid_device_io_stop() correctly,
hdev->io_started is false on entry, the guard short-circuits, and
behavior is unchanged.

No Fixes: tag because the affected drivers gained their
hid_device_io_start() calls independently over years; the bug is a
class-wide API misuse rather than a regression from one commit.

Reported-by: syzbot+9eebf5f6544c5e873858@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=9eebf5f6544c5e873858
Signed-off-by: Philipp Weber <kernel@phwe.de>
Signed-off-by: Jiri Kosina <jkosina@suse.com>
This commit is contained in:
Philipp Weber 2026-05-19 15:00:14 +02:00 committed by Jiri Kosina
parent b7556c8e71
commit a4bc415046
1 changed files with 7 additions and 0 deletions
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7
drivers/hid/hid-core.c
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@ -2440,9 +2440,16 @@ EXPORT_SYMBOL_GPL(hid_hw_start);
*
* This is usually called from remove function or from probe when something
* failed and hid_hw_start was called already.
*
* If the caller enabled HID input via hid_device_io_start() and is unwinding
* without an explicit hid_device_io_stop(), quiesce input first so that
* in-flight reports cannot reach handlers (e.g. hidraw_report_event) whose
* backing objects hid_disconnect() is about to free.
*/
void hid_hw_stop(struct hid_device *hdev)
{
if (hdev->io_started)
hid_device_io_stop(hdev);
hid_disconnect(hdev);
hdev->ll_driver->stop(hdev);
}