linux-kernel - Re: [PATCH] scsi: lpfc: Fix a possible data race in lpfc_unregister_fcf

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Message-ID: <6105b8bf9d35ca2906094a0f9a58b5351bc741da.camel@redhat.com>
Date:   Wed, 05 Jul 2023 10:35:08 -0400
From:   Laurence Oberman <loberman@...hat.com>
To:     Tuo Li <islituo@...il.com>, james.smart@...adcom.com,
        dick.kennedy@...adcom.com, jejb@...ux.ibm.com,
        martin.petersen@...cle.com
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        baijiaju1990@...look.com, BassCheck <bass@...a.edu.cn>
Subject: Re: [PATCH] scsi: lpfc: Fix a possible data race in
 lpfc_unregister_fcf_rescan()

On Fri, 2023-06-30 at 10:47 +0800, Tuo Li wrote:
> The variable phba->fcf.fcf_flag is often protected by the lock 
> phba->hbalock() when is accessed. Here is an example in 
> lpfc_unregister_fcf_rescan():
> 
>   spin_lock_irq(&phba->hbalock);
>   phba->fcf.fcf_flag |= FCF_INIT_DISC;
>   spin_unlock_irq(&phba->hbalock);
> 
> However, in the same function, phba->fcf.fcf_flag is assigned with 0 
> without holding the lock, and thus can cause a data race:
> 
>   phba->fcf.fcf_flag = 0;
> 
> To fix this possible data race, a lock and unlock pair is added when 
> accessing the variable phba->fcf.fcf_flag.
> 
> Reported-by: BassCheck <bass@...a.edu.cn>
> Signed-off-by: Tuo Li <islituo@...il.com>
> ---
>  drivers/scsi/lpfc/lpfc_hbadisc.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/scsi/lpfc/lpfc_hbadisc.c
> b/drivers/scsi/lpfc/lpfc_hbadisc.c
> index 5ba3a9ad9501..9d2feb69cae7 100644
> --- a/drivers/scsi/lpfc/lpfc_hbadisc.c
> +++ b/drivers/scsi/lpfc/lpfc_hbadisc.c
> @@ -6961,7 +6961,9 @@ lpfc_unregister_fcf_rescan(struct lpfc_hba
> *phba)
>         if (rc)
>                 return;
>         /* Reset HBA FCF states after successful unregister FCF */
> +       spin_lock_irq(&phba->hbalock);
>         phba->fcf.fcf_flag = 0;
> +       spin_unlock_irq(&phba->hbalock);
>         phba->fcf.current_rec.flag = 0;
>  
>         /*

This makes sense and looks good to me
Reviewed-by: Laurence Oberman <loberman@...hat.com>