HID: uclogic: fix use-after-free of inrange_timer on remove

Overview

In the Linux kernel, the following vulnerability has been resolved:

HID: uclogic: fix use-after-free of inrange_timer on remove

uclogic_remove() cancels the pen in-range timer and then stops the device:

timer_delete_sync(&drvdata->inrange_timer);
hid_hw_stop(hdev);

timer_delete_sync() only guarantees the timer is idle at that instant. uclogic_raw_event_pen() keeps delivering pen reports until hid_hw_stop() stops the transport several lines later, and every report with pen->inrange == UCLOGIC_PARAMS_PEN_INRANGE_NONE re-arms the timer:

mod_timer(&drvdata->inrange_timer, jiffies + msecs_to_jiffies(100));

A report landing between the timer_delete_sync() call and the transport teardown in hid_hw_stop() re-arms inrange_timer after it was cancelled. uclogic_remove() then returns and the devm drvdata is freed, while hid_hw_stop() has already freed the input device drvdata->pen_input points at, so when the timer fires ~100 ms later uclogic_inrange_timeout() dereferences freed memory -- a use-after-free in timer-softirq context.

Swapping the two calls is not a fix: stopping the device first frees drvdata->pen_input via hidinput_disconnect() while the timer may still be pending, so a timer already armed before removal fires on the freed input device in the window before timer_delete_sync() runs.

Use timer_shutdown_sync() before hid_hw_stop() instead. It cancels the timer, waits for a running callback while pen_input is still valid, and prevents any further re-arming -- a later mod_timer() from an in-flight report is silently ignored -- so the timer is provably dead before hid_hw_stop() frees the inputs. This is the ordering the timer core documents for this "timer re-armed from another path" teardown case.

Affected

• Linux >= 01309e29eb95c16bd48984f2589fad0cbf5e27d1 < f40243358b407aec362fe305fabfcdc94a3abd89
• Linux >= 01309e29eb95c16bd48984f2589fad0cbf5e27d1 < dc5108f18f58870a8dd4203a02a47e571a2be7f0
• Linux >= 01309e29eb95c16bd48984f2589fad0cbf5e27d1 < 9d77ac82e57ead056cf3f71d347083ed9244ad90
• Linux >= 01309e29eb95c16bd48984f2589fad0cbf5e27d1 < e750cdb6de009aace3c77f37fe2173f96175e8e4
• Linux >= 01309e29eb95c16bd48984f2589fad0cbf5e27d1 < 849e537160bbb77fe419ecc3944bfe125dcd441b
• Linux >= 01309e29eb95c16bd48984f2589fad0cbf5e27d1 < f1b3ca06380531f49f988f4721d3ed30b0d7a5d2
• Linux >= 01309e29eb95c16bd48984f2589fad0cbf5e27d1 < f13d0a00204b05e62336da0ab72ea0d87b56690c
• Linux >= 01309e29eb95c16bd48984f2589fad0cbf5e27d1 < 506fd50a9027340f0e9dcc587d10ccb03312dba6
• Linux 5.1

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.