[dm-devel] [PATCH] dm-mpath-rdac.c init race

["Bryn M. Reeves" <breeves redhat com>]

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The current dm-mpath-rdac has a race in the init function since the hw
handler is registered with DM core before allocating the workqueue.

This patch just re-orders the allocation to be before the call to
dm_register_hw_handler and adds calls to destroys the workqueue in error
paths.

Cheers,
Bryn.
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Re-order the initialisation of dm-rdac to avoid registering the hw
handler before the workqueue has been initialised. Closes a race
that would potentially give an oops.

Signed-off-by: Bryn M. Reeves <breeves redhat com>

diff --git a/drivers/md/Makefile b/drivers/md/Makefile
diff --git a/drivers/md/dm-mpath-rdac.c b/drivers/md/dm-mpath-rdac.c
index 16b1613..a3d9d67 100644
--- a/drivers/md/dm-mpath-rdac.c
+++ b/drivers/md/dm-mpath-rdac.c
@@ -664,20 +664,21 @@ static struct hw_handler_type rdac_handler = {
 
 static int __init rdac_init(void)
 {
-	int r = dm_register_hw_handler(&rdac_handler);
-
-	if (r < 0) {
-		DMERR("%s: register failed %d", RDAC_DM_HWH_NAME, r);
-		return r;
-	}
+	int r;	
 
 	rdac_wkqd = create_singlethread_workqueue("rdac_wkqd");
 	if (!rdac_wkqd) {
 		DMERR("Failed to create workqueue rdac_wkqd.");
-		dm_unregister_hw_handler(&rdac_handler);
 		return -ENOMEM;
 	}
 
+	r = dm_register_hw_handler(&rdac_handler);
+	if (r < 0) {
+		DMERR("%s: register failed %d", RDAC_DM_HWH_NAME, r);
+		destroy_workqueue(rdac_wkqd);
+		return r;
+	}
+
 	DMINFO("%s: version %s loaded", RDAC_DM_HWH_NAME, RDAC_DM_HWH_VER);
 	return 0;
 }