Re: [PATCH v4 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.  Releasing one of the three stale keys takes the
> key-release path, because the key still tests positive in reset_keybit, so
> reset_seq_cnt is decremented for a key that was never counted and goes
> [ ... ]
> single-keypress reboot described there would reach every device rather
> than only those that have never parsed a sequence.
> 
> Fixes: 154b7a489a5b ("Input: sysrq - allow specifying alternate reset sequence")
> Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261030045854.153556-2-zhanxusheng1024@gmail.com?part=2