linux-kernel - [PATCH] firewire: fw-sbp2: fix another small generation access bug

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Date:	Sat, 9 Aug 2008 20:22:17 +0200 (CEST)
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	linux1394-devel@...ts.sourceforge.net
cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] firewire: fw-sbp2: fix another small generation access bug

queuecommand() looked at the remote and local node IDs before it read
the bus generation.  The corresponding race with sbp2_reconnect updating
these data was probably impossible to happen though because the current
code blocks the SCSI layer during reconnection.  However, better safe
than sorry, especially if someone later improves the code to not block
the SCSI layer.

Signed-off-by: Stefan Richter <stefanr@...6.in-berlin.de>
---
 drivers/firewire/fw-sbp2.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

Index: linux-2.6.27-rc2/drivers/firewire/fw-sbp2.c
===================================================================
--- linux-2.6.27-rc2.orig/drivers/firewire/fw-sbp2.c
+++ linux-2.6.27-rc2/drivers/firewire/fw-sbp2.c
@@ -1430,7 +1430,7 @@ static int sbp2_scsi_queuecommand(struct
 	struct fw_device *device = fw_device(lu->tgt->unit->device.parent);
 	struct sbp2_command_orb *orb;
 	unsigned int max_payload;
-	int retval = SCSI_MLQUEUE_HOST_BUSY;
+	int generation, retval = SCSI_MLQUEUE_HOST_BUSY;
 
 	/*
 	 * Bidirectional commands are not yet implemented, and unknown
@@ -1474,6 +1474,9 @@ static int sbp2_scsi_queuecommand(struct
 	if (cmd->sc_data_direction == DMA_FROM_DEVICE)
 		orb->request.misc |= cpu_to_be32(COMMAND_ORB_DIRECTION);
 
+	generation = device->generation;
+	smp_rmb();    /* sbp2_map_scatterlist looks at tgt->address_high */
+
 	if (scsi_sg_count(cmd) && sbp2_map_scatterlist(orb, device, lu) < 0)
 		goto out;
 
@@ -1486,7 +1489,7 @@ static int sbp2_scsi_queuecommand(struct
 	if (dma_mapping_error(device->card->device, orb->base.request_bus))
 		goto out;
 
-	sbp2_send_orb(&orb->base, lu, lu->tgt->node_id, lu->generation,
+	sbp2_send_orb(&orb->base, lu, lu->tgt->node_id, generation,
 		      lu->command_block_agent_address + SBP2_ORB_POINTER);
 	retval = 0;
  out:

-- 
Stefan Richter
-=====-==--- =--- -=--=
http://arcgraph.de/sr/

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