genetlink/pmcraid: use proper genetlink multicast API

The pmcraid driver is abusing the genetlink API and is using its
family ID as the multicast group ID, which is invalid and may
belong to somebody else (and likely will.)

Make it use the correct API, but since this may already be used
as-is by userspace, reserve a family ID for this code and also
reserve that group ID to not break userspace assumptions.

My previous patch broke event delivery in the driver as I missed
that it wasn't using the right API and forgot to update it later
in my series.

While changing this, I noticed that the genetlink code could use
the static group ID instead of a strcmp(), so also do that for
the VFS_DQUOT family.

Cc: Anil Ravindranath <anil_ravindranath@pmc-sierra.com>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 15 insertions, 5 deletions

diff --git a/drivers/scsi/pmcraid.c b/drivers/scsi/pmcraid.c
index bd6f743d87a7..892ea6161376 100644
--- a/drivers/scsi/pmcraid.c
+++ b/drivers/scsi/pmcraid.c
@@ -1404,11 +1404,22 @@ enum {
 };
 #define PMCRAID_AEN_CMD_MAX (__PMCRAID_AEN_CMD_MAX - 1)
 
+static struct genl_multicast_group pmcraid_mcgrps[] = {
+	{ .name = "events", /* not really used - see ID discussion below */ },
+};
+
 static struct genl_family pmcraid_event_family = {
-	.id = GENL_ID_GENERATE,
+	/*
+	 * Due to prior multicast group abuse (the code having assumed that
+	 * the family ID can be used as a multicast group ID) we need to
+	 * statically allocate a family (and thus group) ID.
+	 */
+	.id = GENL_ID_PMCRAID,
 	.name = "pmcraid",
 	.version = 1,
-	.maxattr = PMCRAID_AEN_ATTR_MAX
+	.maxattr = PMCRAID_AEN_ATTR_MAX,
+	.mcgrps = pmcraid_mcgrps,
+	.n_mcgrps = ARRAY_SIZE(pmcraid_mcgrps),
 };
 
 /**
@@ -1511,9 +1522,8 @@ static int pmcraid_notify_aen(
 		return result;
 	}
 
-	result =
-		genlmsg_multicast(&pmcraid_event_family, skb, 0,
-				  pmcraid_event_family.id, GFP_ATOMIC);
+	result = genlmsg_multicast(&pmcraid_event_family, skb,
+				   0, 0, GFP_ATOMIC);
 
 	/* If there are no listeners, genlmsg_multicast may return non-zero
 	 * value.