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From:   Chengfeng Ye <dg573847474@gmail.com>
To:     chenxiang66@hisilicon.com, jejb@linux.ibm.com,
        martin.petersen@oracle.com
Cc:     linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org,
        Chengfeng Ye <dg573847474@gmail.com>
Subject: [PATCH] scsi: hisi_sas: Fix potential deadlock on &hisi_hba->lock
Date:   Wed, 28 Jun 2023 15:30:10 +0000
Message-Id: <20230628153010.57705-1-dg573847474@gmail.com>
Precedence: bulk

As &hisi_hba->lock is acquired by hard irq int_abnormal_v1_hw(),
other acquisition of the same lock under process context should
disable irq, otherwise deadlock could happen if the
irq preempt the execution while the lock is held in process context
on the same CPU.

[Interrupt]: int_abnormal_v1_hw()
    -->/root/linux/drivers/scsi/hisi_sas/hisi_sas_v1_hw.c:1447
    -->/root/linux/drivers/scsi/hisi_sas/hisi_sas_main.c:2050
    -->/root/linux/drivers/scsi/hisi_sas/hisi_sas_main.c:1079
    -->spin_lock_irqsave(&hisi_hba->lock, flags);

[Process Context]: hisi_sas_clear_nexus_ha()
    -->/root/linux/drivers/scsi/hisi_sas/hisi_sas_main.c:1932
    -->/root/linux/drivers/scsi/hisi_sas/hisi_sas_main.c:1135
    -->/root/linux/drivers/scsi/hisi_sas/hisi_sas_main.c:1116
    -->/root/linux/drivers/scsi/hisi_sas/hisi_sas_main.c:1105
    -->/root/linux/drivers/scsi/hisi_sas/hisi_sas_main.c:166
    -->spin_lock(&hisi_hba->lock);

[Process Context]: hisi_sas_dev_found()
    -->/root/linux/drivers/scsi/hisi_sas/hisi_sas_main.c:665
    -->spin_lock(&hisi_hba->lock);

[Process Context]: hisi_sas_queue_command()
    -->/root/linux/drivers/scsi/hisi_sas/hisi_sas_main.c:188
    -->spin_lock(&hisi_hba->lock);

This flaw was found by an experimental static analysis tool I am
developing for irq-related deadlock, which reported the above
warning when analyzing the linux kernel 6.4-rc7 release.

The tentative patch fix the potential deadlock by spin_lock_irqsave().

Signed-off-by: Chengfeng Ye <dg573847474@gmail.com>
---
 drivers/scsi/hisi_sas/hisi_sas_main.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/scsi/hisi_sas/hisi_sas_main.c b/drivers/scsi/hisi_sas/hisi_sas_main.c
index 412431c901a7..47c5062a732e 100644
--- a/drivers/scsi/hisi_sas/hisi_sas_main.c
+++ b/drivers/scsi/hisi_sas/hisi_sas_main.c
@@ -161,11 +161,12 @@ static void hisi_sas_slot_index_clear(struct hisi_hba *hisi_hba, int slot_idx)
 
 static void hisi_sas_slot_index_free(struct hisi_hba *hisi_hba, int slot_idx)
 {
+	unsigned long flags;
 	if (hisi_hba->hw->slot_index_alloc ||
 	    slot_idx < HISI_SAS_RESERVED_IPTT) {
-		spin_lock(&hisi_hba->lock);
+		spin_lock_irqsave(&hisi_hba->lock, flags);
 		hisi_sas_slot_index_clear(hisi_hba, slot_idx);
-		spin_unlock(&hisi_hba->lock);
+		spin_unlock_irqrestore(&hisi_hba->lock, flags);
 	}
 }
 
@@ -181,11 +182,12 @@ static int hisi_sas_slot_index_alloc(struct hisi_hba *hisi_hba,
 {
 	int index;
 	void *bitmap = hisi_hba->slot_index_tags;
+	unsigned long flags;
 
 	if (rq)
 		return rq->tag + HISI_SAS_RESERVED_IPTT;
 
-	spin_lock(&hisi_hba->lock);
+	spin_lock_irqsave(&hisi_hba->lock, flags);
 	index = find_next_zero_bit(bitmap, HISI_SAS_RESERVED_IPTT,
 				   hisi_hba->last_slot_index + 1);
 	if (index >= HISI_SAS_RESERVED_IPTT) {
@@ -193,13 +195,13 @@ static int hisi_sas_slot_index_alloc(struct hisi_hba *hisi_hba,
 				HISI_SAS_RESERVED_IPTT,
 				0);
 		if (index >= HISI_SAS_RESERVED_IPTT) {
-			spin_unlock(&hisi_hba->lock);
+			spin_unlock_irqrestore(&hisi_hba->lock, flags);
 			return -SAS_QUEUE_FULL;
 		}
 	}
 	hisi_sas_slot_index_set(hisi_hba, index);
 	hisi_hba->last_slot_index = index;
-	spin_unlock(&hisi_hba->lock);
+	spin_unlock_irqrestore(&hisi_hba->lock, flags);
 
 	return index;
 }
@@ -658,11 +660,12 @@ static struct hisi_sas_device *hisi_sas_alloc_dev(struct domain_device *device)
 {
 	struct hisi_hba *hisi_hba = dev_to_hisi_hba(device);
 	struct hisi_sas_device *sas_dev = NULL;
+	unsigned long flags;
 	int last = hisi_hba->last_dev_id;
 	int first = (hisi_hba->last_dev_id + 1) % HISI_SAS_MAX_DEVICES;
 	int i;
 
-	spin_lock(&hisi_hba->lock);
+	spin_lock_irqsave(&hisi_hba->lock, flags);
 	for (i = first; i != last; i %= HISI_SAS_MAX_DEVICES) {
 		if (hisi_hba->devices[i].dev_type == SAS_PHY_UNUSED) {
 			int queue = i % hisi_hba->queue_count;
@@ -682,7 +685,7 @@ static struct hisi_sas_device *hisi_sas_alloc_dev(struct domain_device *device)
 		i++;
 	}
 	hisi_hba->last_dev_id = i;
-	spin_unlock(&hisi_hba->lock);
+	spin_unlock_irqrestore(&hisi_hba->lock, flags);
 
 	return sas_dev;
 }
-- 
2.17.1