HID: uclogic: fix use-after-free of inrange_timer on remove
3Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackepss 0.2%
exploitation probability
0.2%top 93% of all CVEs
observed exploitation
nono source reports it
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 products
Linux · LinuxReferences
https://git.kernel.org/stable/c/506fd50a9027340f0e9dcc587d10ccb03312dba6https://git.kernel.org/stable/c/849e537160bbb77fe419ecc3944bfe125dcd441bhttps://git.kernel.org/stable/c/9d77ac82e57ead056cf3f71d347083ed9244ad90https://git.kernel.org/stable/c/dc5108f18f58870a8dd4203a02a47e571a2be7f0https://git.kernel.org/stable/c/e750cdb6de009aace3c77f37fe2173f96175e8e4https://git.kernel.org/stable/c/f13d0a00204b05e62336da0ab72ea0d87b56690chttps://git.kernel.org/stable/c/f1b3ca06380531f49f988f4721d3ed30b0d7a5d2https://git.kernel.org/stable/c/f40243358b407aec362fe305fabfcdc94a3abd89