Re: [PATCH v3 2/2] tty: sysrq: reset the per-device key state when reparsing reset_seq

[sashiko-bot@kernel.org]

> From: Zhan Xusheng <zhanxusheng@xiaomi.com>
> 
> sysrq_parse_reset_sequence() clears reset_seq_cnt, but reset_keybit is
> only ever __set_bit() and reset_seq_len only ever incremented.  struct
> sysrq_state is allocated once per input device in sysrq_connect() and
> lives until the device goes away, so both accumulate every time the
> sequence is reparsed, which happens whenever the mode 0644 reset_seq
> parameter is written.
> 
> After writing 56,29,111 and then 59,60 a device keeps all five keys in
> reset_keybit with reset_seq_len 5, so the effective combination is the
> union of the old and the new sequence.  Holding just 59 and 60 counts two
> of five and does nothing, while releasing a stale key drives
> reset_seq_cnt below zero.
> 
> Clear both along with reset_seq_cnt.  Also delete keyreset_timer: with
> sysrq_downtime_ms set, holding a full sequence arms it, and it is only
> deleted on a press outside the sequence or a release inside it.  Dropping
> the old keys from reset_keybit removes both of those cancellations, so an
> already armed reset would survive into orderly_reboot().
> 
> Fixes: 154b7a489a5b ("Input: sysrq - allow specifying alternate reset sequence")
> Cc: stable@vger.kernel.org
> Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>

Sashiko has reviewed this patch and found no issues.

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