linux-kernel - [BUG] fs: dlm: possible ABBA deadlock

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Message-ID: <79f8d302-f53f-3891-965a-bcb460ab15ca@gmail.com>
Date:   Thu, 19 Aug 2021 16:54:57 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     ccaulfie@...hat.com, teigland@...hat.com
Cc:     cluster-devel@...hat.com,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: [BUG] fs: dlm: possible ABBA deadlock

Hello,

My static analysis tool reports a possible ABBA deadlock in the dlm 
filesystem in Linux 5.10:

dlm_recover_waiters_pre()
   mutex_lock(&ls->ls_waiters_mutex); --> line 5130
   recover_convert_waiter()
     _receive_convert_reply()
       lock_rsb()
         mutex_lock(&r->res_mutex); --> line 69

dlm_recover_waiters_post()
   lock_rsb()
     mutex_lock(&r->res_mutex); --> line 69
   mutex_lock(&ls->ls_waiters_mutex); --> line 5307

When dlm_recover_waiters_pre() and dlm_recover_waiters_post() are 
concurrently executed, the deadlock can occur.

I am not quite sure whether this possible deadlock is real and how to 
fix it if it is real.
Any feedback would be appreciated, thanks :)

Reported-by: TOTE Robot <oslab@...nghua.edu.cn>

Best wishes,
Jia-Ju Bai