From 506fd50a9027340f0e9dcc587d10ccb03312dba6 Mon Sep 17 00:00:00 2001 From: Ibrahim Hashimov Date: Tue, 14 Jul 2026 19:39:46 +0200 Subject: [PATCH] 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. Fixes: 01309e29eb95 ("HID: uclogic: Support in-range reporting emulation") Cc: stable@vger.kernel.org Signed-off-by: Ibrahim Hashimov Assisted-by: AuditCode-AI:2026.07 Signed-off-by: Jiri Kosina --- drivers/hid/hid-uclogic-core.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/hid/hid-uclogic-core.c b/drivers/hid/hid-uclogic-core.c index b73f09d26688..0b8a83fa6c5b 100644 --- a/drivers/hid/hid-uclogic-core.c +++ b/drivers/hid/hid-uclogic-core.c @@ -548,7 +548,17 @@ static void uclogic_remove(struct hid_device *hdev) { struct uclogic_drvdata *drvdata = hid_get_drvdata(hdev); - timer_delete_sync(&drvdata->inrange_timer); + /* + * Shut the in-range timer down before stopping the device. + * uclogic_raw_event_pen() re-arms inrange_timer on every pen report + * and keeps running until hid_hw_stop() stops the transport, so a + * plain timer_delete_sync() here can be undone by a report landing in + * the window before hid_hw_stop(). timer_shutdown_sync() cancels the + * timer and makes any later re-arm a no-op, so it is provably dead + * before hid_hw_stop() frees the input device drvdata->pen_input + * points at. + */ + timer_shutdown_sync(&drvdata->inrange_timer); hid_hw_stop(hdev); kfree(drvdata->desc_ptr); uclogic_params_cleanup(&drvdata->params);