Re: [PATCH] Input: sysrq - reset the per-device key state when reparsing reset_seq

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] tty: sysrq: uncancelable reset timer on sequence change
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commit 2166ad442fbe41cfd64e5275427188db06092a2e
Author: Zhan Xusheng <zhanxusheng1024@gmail.com>

Input: sysrq - reset the per-device key state when reparsing reset_seq

This commit clears the accumulated reset_seq_len and reset_keybit state when
reparsing the reset sequence. This prevents stale keys from affecting the reset
detection, as the previous code only cleared reset_seq_cnt.

> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> index c2e4b31b699aa..d28a4726b07fc 100644
> --- a/drivers/tty/sysrq.c
> +++ b/drivers/tty/sysrq.c
> @@ -689,6 +689,8 @@ static void sysrq_parse_reset_sequence(struct sysrq_state *state)
>  	int i;
>  	unsigned short key;
>  
> +	bitmap_zero(state->reset_keybit, KEY_CNT);
> +	state->reset_seq_len = 0;
>  	state->reset_seq_cnt = 0;
>  
>  	for (i = 0; i < sysrq_reset_seq_len; i++) {

[Severity: Medium]
Does clearing the reset_keybit here create a situation where the reset timer
becomes uncancelable if the sequence changes while keys are held?

If sysrq_reset_downtime_ms is configured and a user is currently holding the
reset sequence keys, the reset timer will be active.  If the sequence is then
modified via sysfs, this function clears the old reset_keybit.

When the user subsequently releases the old keys:

drivers/tty/sysrq.c:sysrq_detect_reset_sequence() {
    if (!test_bit(code, state->reset_keybit)) {
        /* ... */
        if (value && state->reset_seq_cnt) {
            state->reset_canceled = true;
            timer_delete(&state->keyreset_timer);
        }
    } else if (value == 0) {
        ...
}

Because the key is no longer in reset_keybit, it takes the first branch.
Since this is a key release (value == 0), the timer_delete() is skipped,
leaving the timer active and potentially causing an unwanted system reboot.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261016032732.2328852-1-zhanxusheng@xiaomi.com?part=1