linux-kernel - Re: [BUG] scsi/qla2xxx: a possible sleep-in-atomic bug in qlt_get

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Date:   Tue, 12 Dec 2017 20:42:01 -0800
From:   James Bottomley <jejb@...ux.vnet.ibm.com>
To:     Jia-Ju Bai <baijiaju1990@...il.com>, qla2xxx-upstream@...gic.com,
        martin.petersen@...cle.com
Cc:     linux-scsi@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] scsi/qla2xxx: a possible sleep-in-atomic bug in
 qlt_get_tag

On Wed, 2017-12-13 at 11:18 +0800, Jia-Ju Bai wrote:
> The driver may sleep under a spinlock.
> The function call paths are:
> qlt_handle_abts_recv_work (acquire the spinlock)
>    qlt_response_pkt_all_vps
>      qlt_response_pkt
>        qlt_handle_cmd_for_atio
>          qlt_get_tag
>            percpu_ida_alloc --> may sleep
> 
> qla82xx_msix_rsp_q (acquire the spinlock)
>    qla24xx_process_response_queue
>      qlt_handle_abts_recv
>        qlt_response_pkt_all_vps
>          qlt_response_pkt
>            qlt_handle_cmd_for_atio
>              qlt_get_tag
>                percpu_ida_alloc --> may sleep-in-atomic
> 
> qla24xx_intr_handler (acquire the spinlock)
>    qla24xx_process_response_queue
>      qlt_handle_abts_recv
>        qlt_response_pkt
>          qlt_handle_cmd_for_atio
>            qlt_get_tag
>              percpu_ida_alloc --> may sleep
> 
> I do not find a good way to fix it, so I only report.
> This possible bug is found by my static analysis tool (DSAC) and
> checked by my code review.

The report is incorrect: percpu_ida_alloc with state==TASK_RUNNING is
atomic (and interrupt) safe which appears to be the case here.

James