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Subject[PATCH 2/2] [SCSI] pm8001: Fix possible racing codition.
Date
From: Santosh Nayak <santoshprasadnayak@gmail.com>

There is a possble racing scenario.

'process_oq' is called by two routines, as shown below.

pm8001_8001_dispatch = {
.......
.isr = pm8001_chip_isr --> process_oq,// A
.isr_process_oq = process_oq, // B
.....
}
process_oq() --> process_one_iomb() --> mpi_sata_completion()

In 'mpi_sata_completion', "pm8001_ha->lock" is first released.
It means lock is taken before, which is true for
the context A, as 'pm8001_ha->lock' is taken in 'pm8001_chip_isr()'

But for context B there is no lock taken before and pm8001_ha->lock
is unlocked in 'mpi_sata_completion()'. This may unlock the lock
taken in context A. Possible racing ??

If 'pm8001_ha->lock' is taken in 'process_oq()' instead of
'pm8001_chip_isr' then the above issue can be avoided.

Signed-off-by: Santosh Nayak <santoshprasadnayak@gmail.com>
---
drivers/scsi/pm8001/pm8001_hwi.c | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/scsi/pm8001/pm8001_hwi.c b/drivers/scsi/pm8001/pm8001_hwi.c
index 838e3e2..6d9973b 100644
--- a/drivers/scsi/pm8001/pm8001_hwi.c
+++ b/drivers/scsi/pm8001/pm8001_hwi.c
@@ -3663,7 +3663,9 @@ static int process_oq(struct pm8001_hba_info *pm8001_ha)
void *pMsg1 = NULL;
u8 uninitialized_var(bc);
u32 ret = MPI_IO_STATUS_FAIL;
+ unsigned long flags;

+ spin_lock_irqsave(&pm8001_ha->lock, flags);
circularQ = &pm8001_ha->outbnd_q_tbl[0];
do {
ret = mpi_msg_consume(pm8001_ha, circularQ, &pMsg1, &bc);
@@ -3682,6 +3684,7 @@ static int process_oq(struct pm8001_hba_info *pm8001_ha)
break;
}
} while (1);
+ spin_unlock_irqrestore(&pm8001_ha->lock, flags);
return ret;
}

@@ -4087,12 +4090,9 @@ static u32 pm8001_chip_is_our_interupt(struct pm8001_hba_info *pm8001_ha)
static irqreturn_t
pm8001_chip_isr(struct pm8001_hba_info *pm8001_ha)
{
- unsigned long flags;
- spin_lock_irqsave(&pm8001_ha->lock, flags);
pm8001_chip_interrupt_disable(pm8001_ha);
process_oq(pm8001_ha);
pm8001_chip_interrupt_enable(pm8001_ha);
- spin_unlock_irqrestore(&pm8001_ha->lock, flags);
return IRQ_HANDLED;
}

--
1.7.4.4


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