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

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Message-Id: <20230630024748.1035993-1-islituo@gmail.com>
Date:   Fri, 30 Jun 2023 10:47:48 +0800
From:   Tuo Li <islituo@...il.com>
To:     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, Tuo Li <islituo@...il.com>,
        BassCheck <bass@...a.edu.cn>
Subject: [PATCH] scsi: lpfc: Fix a possible data race in lpfc_unregister_fcf_rescan()

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