linux-kernel - Re: [BUG] ALSA: core: seq: a possible double-lock bug in snd_seq_midisynth

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Message-ID: <s5hd0htpezg.wl-tiwai@suse.de>
Date:   Mon, 29 Jul 2019 07:49:23 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     perex@...ex.cz, gregkh@...uxfoundation.org, rfontana@...hat.com,
        allison@...utok.net, tglx@...utronix.de,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [BUG] ALSA: core: seq: a possible double-lock bug in snd_seq_midisynth_remove()

On Mon, 29 Jul 2019 05:54:07 +0200,
Jia-Ju Bai wrote:
> 
> In snd_seq_midisynth_remove(), there is a possible double-lock bug:
> snd_seq_midisynth_remove()
>     mutex_lock(&register_mutex); -- line 421
>     snd_seq_delete_kernel_client() --- line 436
>         seq_free_client() -- line 2244
>             mutex_lock(&register_mutex); -- line 294
> 
> This bug is found by a static analysis tool STCheck written by us.

No, it's a false-positive report.  Both register_mutex's are
static, hence they are local to each file.  That is, you're looking at
two different mutexes.


Takashi