Affected: Linux

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

usb: ljca: bound bank_num in ljca_enumerate_gpio()

ljca_enumerate_gpio() reads desc->bank_num from the device and loops valid_pin[i] = get_unaligned_le32(...) for i < bank_num. valid_pin[] holds only LJCA_MAX_GPIO_NUM / 32 = 2 entries.

Two checks run before the loop. The reply length must match struct_size(desc, bank_desc, bank_num). The product pins_per_bank * bank_num must not exceed LJCA_MAX_GPIO_NUM. Neither one bounds bank_num against the size of valid_pin[]. The reply is capped at LJCA_MAX_PAYLOAD_SIZE (60) bytes, so the struct_size check limits bank_num to 9. A device that reports bank_num 9 with pins_per_bank 7 still passes both checks. gpio_num is 63 and the reply is 56 bytes. The loop then writes nine u32 into the two entry array and overruns valid_pin[] on the stack.

A broken or malicious LJCA device can therefore overflow the stack. Reject a bank_num that does not fit valid_pin[].