Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Jia-Ju Bai <baijiaju1990@gmail.com>
Subject: [BUG] fs: dlm: possible ABBA deadlock
To:     ccaulfie@redhat.com, teigland@redhat.com
Cc:     cluster-devel@redhat.com,
        linux-kernel <linux-kernel@vger.kernel.org>
Message-ID: <79f8d302-f53f-3891-965a-bcb460ab15ca@gmail.com>
Date:   Thu, 19 Aug 2021 16:54:57 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101
 Thunderbird/68.4.1
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Precedence: bulk

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@tsinghua.edu.cn>


Best wishes,
Jia-Ju Bai