netlink: make nlmsg_end() and genlmsg_end() void

Contrary to common expectations for an "int" return, these functions
return only a positive value -- if used correctly they cannot even
return 0 because the message header will necessarily be in the skb.

This makes the very common pattern of

  if (genlmsg_end(...) < 0) { ... }

be a whole bunch of dead code. Many places also simply do

  return nlmsg_end(...);

and the caller is expected to deal with it.

This also commonly (at least for me) causes errors, because it is very
common to write

  if (my_function(...))
    /* error condition */

and if my_function() does "return nlmsg_end()" this is of course wrong.

Additionally, there's not a single place in the kernel that actually
needs the message length returned, and if anyone needs it later then
it'll be very easy to just use skb->len there.

Remove this, and make the functions void. This removes a bunch of dead
code as described above. The patch adds lines because I did

-	return nlmsg_end(...);
+	nlmsg_end(...);
+	return 0;

I could have preserved all the function's return values by returning
skb->len, but instead I've audited all the places calling the affected
functions and found that none cared. A few places actually compared
the return value with <= 0 in dump functionality, but that could just
be changed to < 0 with no change in behaviour, so I opted for the more
efficient version.

One instance of the error I've made numerous times now is also present
in net/phonet/pn_netlink.c in the route_dumpit() function - it didn't
check for <0 or <=0 and thus broke out of the loop every single time.
I've preserved this since it will (I think) have caused the messages to
userspace to be formatted differently with just a single message for
every SKB returned to userspace. It's possible that this isn't needed
for the tools that actually use this, but I don't even know what they
are so couldn't test that changing this behaviour would be acceptable.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

7 files changed, 10 insertions, 24 deletions

diff --git a/drivers/acpi/event.c b/drivers/acpi/event.c
index ef2d730734dc..e24ea4e796e4 100644
--- a/drivers/acpi/event.c
+++ b/drivers/acpi/event.c
@@ -100,7 +100,6 @@ int acpi_bus_generate_netlink_event(const char *device_class,
 	struct acpi_genl_event *event;
 	void *msg_header;
 	int size;
-	int result;
 
 	/* allocate memory */
 	size = nla_total_size(sizeof(struct acpi_genl_event)) +
@@ -137,11 +136,7 @@ int acpi_bus_generate_netlink_event(const char *device_class,
 	event->data = data;
 
 	/* send multicast genetlink message */
-	result = genlmsg_end(skb, msg_header);
-	if (result < 0) {
-		nlmsg_free(skb);
-		return result;
-	}
+	genlmsg_end(skb, msg_header);
 
 	genlmsg_multicast(&acpi_event_genl_family, skb, 0, 0, GFP_ATOMIC);
 	return 0;
diff --git a/drivers/net/ethernet/rocker/rocker.c b/drivers/net/ethernet/rocker/rocker.c
index 964d719b150f..d54781e71cd4 100644
--- a/drivers/net/ethernet/rocker/rocker.c
+++ b/drivers/net/ethernet/rocker/rocker.c
@@ -3674,7 +3674,8 @@ static int rocker_fdb_fill_info(struct sk_buff *skb,
 	if (vid && nla_put_u16(skb, NDA_VLAN, vid))
 		goto nla_put_failure;
 
-	return nlmsg_end(skb, nlh);
+	nlmsg_end(skb, nlh);
+	return 0;
 
 nla_put_failure:
 	nlmsg_cancel(skb, nlh);
diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 6b6b45622a0a..c5f79e7513a6 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -363,7 +363,8 @@ static int vxlan_fdb_info(struct sk_buff *skb, struct vxlan_dev *vxlan,
 	if (nla_put(skb, NDA_CACHEINFO, sizeof(ci), &ci))
 		goto nla_put_failure;
 
-	return nlmsg_end(skb, nlh);
+	nlmsg_end(skb, nlh);
+	return 0;
 
 nla_put_failure:
 	nlmsg_cancel(skb, nlh);
diff --git a/drivers/net/wireless/mac80211_hwsim.c b/drivers/net/wireless/mac80211_hwsim.c
index 494e7335aa64..4a4c6586a8d2 100644
--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -2557,7 +2557,8 @@ static int mac80211_hwsim_get_radio(struct sk_buff *skb,
 	if (res < 0)
 		goto out_err;
 
-	return genlmsg_end(skb, hdr);
+	genlmsg_end(skb, hdr);
+	return 0;
 
 out_err:
 	genlmsg_cancel(skb, hdr);
diff --git a/drivers/scsi/pmcraid.c b/drivers/scsi/pmcraid.c
index 8c27b6a77ec4..cf222f46eac5 100644
--- a/drivers/scsi/pmcraid.c
+++ b/drivers/scsi/pmcraid.c
@@ -1473,13 +1473,7 @@ static int pmcraid_notify_aen(
 	}
 
 	/* send genetlink multicast message to notify appplications */
-	result = genlmsg_end(skb, msg_header);
-
-	if (result < 0) {
-		pmcraid_err("genlmsg_end failed\n");
-		nlmsg_free(skb);
-		return result;
-	}
+	genlmsg_end(skb, msg_header);
 
 	result = genlmsg_multicast(&pmcraid_event_family, skb,
 				   0, 0, GFP_ATOMIC);
diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 1157b559683b..1a1bcf71ec9d 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -784,9 +784,7 @@ static int tcmu_netlink_event(enum tcmu_genl_cmd cmd, const char *name, int mino
 	if (ret < 0)
 		goto free_skb;
 
-	ret = genlmsg_end(skb, msg_header);
-	if (ret < 0)
-		goto free_skb;
+	genlmsg_end(skb, msg_header);
 
 	ret = genlmsg_multicast(&tcmu_genl_family, skb, 0,
 				TCMU_MCGRP_CONFIG, GFP_KERNEL);
diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 87e0b0782023..48491d1a81d6 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -1759,11 +1759,7 @@ int thermal_generate_netlink_event(struct thermal_zone_device *tz,
 	thermal_event->event = event;
 
 	/* send multicast genetlink message */
-	result = genlmsg_end(skb, msg_header);
-	if (result < 0) {
-		nlmsg_free(skb);
-		return result;
-	}
+	genlmsg_end(skb, msg_header);
 
 	result = genlmsg_multicast(&thermal_event_genl_family, skb, 0,
 				   0, GFP_ATOMIC);