AZL-97709

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

Input: hynitron_cstxxx - validate touch count and finger IDs

The driver allocates maxtouchnum input slots, which are indexed from zero through maxtouchnum - 1. The current check allows a finger ID equal to maxtouchnum to reach cst3xxreportcontact(). While the input core ignores out-of-range slot indices, reporting touch data without a valid slot change corrupts the touch state of the previously active slot.

The touch count is read from the controller's report and is used to index the fixed-size report buffer without first checking its range. Reject counts larger than the supported number of touch slots before checking the trailing byte or parsing touch data.

Reject finger IDs equal to or greater than maxtouchnum, and return immediately when an invalid finger ID is encountered so that corrupt touch frames are discarded instead of reporting partial contact state.

The V821 Avaota F1 board configures the vendor driver with one touch slot, so finger ID 1 is already invalid on that device.