linux-kernel - [BUG] scsi: qedi: possible ABBA deadlock in qedi_process_tmf_resp() and qedi_process_cmd_cleanup

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Date:   Tue, 8 Feb 2022 19:23:01 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     njavali@...vell.com, mrangankar@...vell.com,
        GR-QLogic-Storage-Upstream@...vell.com, jejb@...ux.ibm.com,
        martin.petersen@...cle.com
Cc:     linux-scsi@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: [BUG] scsi: qedi: possible ABBA deadlock in qedi_process_tmf_resp()
 and qedi_process_cmd_cleanup_resp()

Hello,

My static analysis tool reports a possible ABBA deadlock in the qedi 
driver in Linux 5.16:

qedi_process_tmf_resp()
   spin_lock(&session->back_lock); --> Line 201 (Lock A)
   spin_lock(&qedi_conn->tmf_work_lock); --> Line 230 (Lock B)

qedi_process_cmd_cleanup_resp()
   spin_lock_bh(&qedi_conn->tmf_work_lock); --> Line 752 (Lock B)
   spin_lock_bh(&conn->session->back_lock); --> Line 784 (Lock A)

When qedi_process_tmf_resp() and qedi_process_cmd_cleanup_resp() 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