path: root/net/phonet
diff options
authorJohannes Berg <johannes.berg@intel.com>2015-01-16 22:09:00 +0100
committerDavid S. Miller <davem@davemloft.net>2015-01-18 01:03:45 -0500
commit053c095a82cf773075e83d7233b5cc19a1f73ece (patch)
treec787028efa9a73a182a0f338f87b6294cef4b8b9 /net/phonet
parentede58ef28e105de94475b2b69fa069c9a2ce6933 (diff)
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>
Diffstat (limited to 'net/phonet')
1 files changed, 11 insertions, 5 deletions
diff --git a/net/phonet/pn_netlink.c b/net/phonet/pn_netlink.c
index b64151ade6b3..54d766842c2b 100644
--- a/net/phonet/pn_netlink.c
+++ b/net/phonet/pn_netlink.c
@@ -121,7 +121,8 @@ static int fill_addr(struct sk_buff *skb, struct net_device *dev, u8 addr,
ifm->ifa_index = dev->ifindex;
if (nla_put_u8(skb, IFA_LOCAL, addr))
goto nla_put_failure;
- return nlmsg_end(skb, nlh);
+ nlmsg_end(skb, nlh);
+ return 0;
nlmsg_cancel(skb, nlh);
@@ -190,7 +191,8 @@ static int fill_route(struct sk_buff *skb, struct net_device *dev, u8 dst,
if (nla_put_u8(skb, RTA_DST, dst) ||
nla_put_u32(skb, RTA_OIF, dev->ifindex))
goto nla_put_failure;
- return nlmsg_end(skb, nlh);
+ nlmsg_end(skb, nlh);
+ return 0;
nlmsg_cancel(skb, nlh);
@@ -282,9 +284,13 @@ static int route_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
if (addr_idx++ < addr_start_idx)
- if (fill_route(skb, dev, addr << 2, NETLINK_CB(cb->skb).portid,
- cb->nlh->nlmsg_seq, RTM_NEWROUTE))
- goto out;
+ fill_route(skb, dev, addr << 2, NETLINK_CB(cb->skb).portid,
+ cb->nlh->nlmsg_seq, RTM_NEWROUTE);
+ /* fill_route() used to return > 0 (or negative errors) but
+ * never 0 - ignore the return value and just go out to
+ * call dumpit again from outside to preserve the behavior
+ */
+ goto out;

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