Affected: Linux

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

irqchip/renesas-rzg2l: Fix loss of interrupt

rzg2l_clear_irq_int() and rzg2l_clear_tint_int() perform a read-modify-write on the ISCR/TSCR status registers to clear the bit for the interrupt just handled. Since these registers are write-0-to-clear per bit, this is racy:

If another interrupt's status bit gets set between the read and the write, that bit is written back as 0 by the software-constructed value, clearing an interrupt that hasn't been serviced yet and losing it.

This can be reproduced by triggering multiple interrupts at once, e.g.:

gpioset -c gpiochip0 355=0 353=0 328=0 352=0

Fix this by writing back only the bit being cleared, with all other bits set to 1, instead of read-modify-writing the whole register. Since 1-bits are left unchanged by hardware, concurrently-set status bits for other interrupts are preserved.