[PATCH AUTOSEL 4.9 24/48] scsi: atari_scsi: Fix race condition between .queuecommand and EH

[Sasha Levin]

From: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>

[ Upstream commit 03fe6a640a05c5dc04b6bcdddfb981d015e84ed4 ]

It is possible that bus_reset_cleanup() or .eh_abort_handler could be
invoked during NCR5380_queuecommand(). If that takes place before the new
command is enqueued and after the ST-DMA "lock" has been acquired, the
ST-DMA "lock" will be released again. This will result in a lost DMA
interrupt and a command timeout. Fix this by excluding EH and interrupt
handlers while the new command is enqueued.

Link: https://lore.kernel.org/r/af25163257796b50bb99d4ede4025cea55787b8f.1605847196.git.fthain@xxxxxxxxxxxxxxxxxxx
Tested-by: Michael Schmitz <schmitzmic@xxxxxxxxx>
Reviewed-by: Michael Schmitz <schmitzmic@xxxxxxxxx>
Signed-off-by: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/scsi/NCR5380.c    |  9 ++++++---
 drivers/scsi/atari_scsi.c | 10 +++-------
 2 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c
index 27270631c70c2..c689b0e8ce4c9 100644
--- a/drivers/scsi/NCR5380.c
+++ b/drivers/scsi/NCR5380.c
@@ -659,11 +659,14 @@ static int NCR5380_queue_command(struct Scsi_Host *instance,
 
 	cmd->result = 0;
 
-	if (!NCR5380_acquire_dma_irq(instance))
-		return SCSI_MLQUEUE_HOST_BUSY;
-
 	spin_lock_irqsave(&hostdata->lock, flags);
 
+	if (!NCR5380_acquire_dma_irq(instance)) {
+		spin_unlock_irqrestore(&hostdata->lock, flags);
+
+		return SCSI_MLQUEUE_HOST_BUSY;
+	}
+
 	/*
 	 * Insert the cmd into the issue queue. Note that REQUEST SENSE
 	 * commands are added to the head of the queue since any command will
diff --git a/drivers/scsi/atari_scsi.c b/drivers/scsi/atari_scsi.c
index 9dc4b689f94b0..de06ce9f18810 100644
--- a/drivers/scsi/atari_scsi.c
+++ b/drivers/scsi/atari_scsi.c
@@ -411,15 +411,11 @@ static int falcon_get_lock(struct Scsi_Host *instance)
 	if (IS_A_TT())
 		return 1;
 
-	if (stdma_is_locked_by(scsi_falcon_intr) &&
-	    instance->hostt->can_queue > 1)
+	if (stdma_is_locked_by(scsi_falcon_intr))
 		return 1;
 
-	if (in_interrupt())
-		return stdma_try_lock(scsi_falcon_intr, instance);
-
-	stdma_lock(scsi_falcon_intr, instance);
-	return 1;
+	/* stdma_lock() may sleep which means it can't be used here */
+	return stdma_try_lock(scsi_falcon_intr, instance);
 }
 
 #ifndef MODULE
-- 
2.27.0