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

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Message-ID: <CABPRKS8_bGqfE3x8abj0p1CTVcLk8EtVn8gjbWd15CaC42_Oew@mail.gmail.com>
Date:   Tue, 4 Jul 2023 09:14:32 -0700
From:   Justin Tee <justintee8345@...il.com>
To:     Tuo Li <islituo@...il.com>
Cc:     james.smart@...adcom.com, dick.kennedy@...adcom.com,
        jejb@...ux.ibm.com, martin.petersen@...cle.com,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        baijiaju1990@...look.com, BassCheck <bass@...a.edu.cn>,
        Justin Tee <justin.tee@...adcom.com>
Subject: Re: [PATCH] scsi: lpfc: Fix a possible data race in lpfc_unregister_fcf_rescan()

Hi Tuo,

Looks good.

Reviewed-by: Justin Tee <justin.tee@...adcom.com>

Thanks,
Justin

On Thu, Jun 29, 2023 at 8:03 PM Tuo Li <islituo@...il.com> 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;
>
>         /*
> --
> 2.34.1
>