WARNING: proc registration bug in clusterip_tg_check

[syzbot]

Hello,

syzbot tried to test the proposed patch but build/boot failed:
kernel build failed: failed to run /usr/bin/make [make bzImage -j 32  
CC=/syzkaller/gcc/bin/gcc]: exit status 2
scripts/kconfig/conf  --silentoldconfig Kconfig
  CHK     include/config/kernel.release
  CHK     include/generated/uapi/linux/version.h
  CHK     include/generated/utsrelease.h
  CHK     scripts/mod/devicetable-offsets.h
  CHK     include/generated/bounds.h
  CHK     include/generated/timeconst.h
  CHK     include/generated/asm-offsets.h
  CALL    scripts/checksyscalls.sh
  CHK     include/generated/compile.h
  CC      net/ipv4/netfilter/ipt_CLUSTERIP.o
  CC      net/ipv4/netfilter/ipt_MASQUERADE.o
  CC      net/ipv4/netfilter/ipt_REJECT.o
  CC      net/ipv4/netfilter/ipt_SYNPROXY.o
  CC      net/ipv4/netfilter/arp_tables.o
  CC      net/ipv4/netfilter/arpt_mangle.o
  CC      net/ipv4/netfilter/arptable_filter.o
  CC      net/ipv4/netfilter/nf_dup_ipv4.o
net/ipv4/netfilter/ipt_CLUSTERIP.c: In function ‘clusterip_config_init’:
net/ipv4/netfilter/ipt_CLUSTERIP.c:253:22: error: expected ‘;’ before ‘:’  
token
   goto err_remove_pte:
                      ^
scripts/Makefile.build:316: recipe for  
target 'net/ipv4/netfilter/ipt_CLUSTERIP.o' failed
make[3]: *** [net/ipv4/netfilter/ipt_CLUSTERIP.o] Error 1
make[3]: *** Waiting for unfinished jobs....
scripts/Makefile.build:575: recipe for target 'net/ipv4/netfilter' failed
make[2]: *** [net/ipv4/netfilter] Error 2
scripts/Makefile.build:575: recipe for target 'net/ipv4' failed
make[1]: *** [net/ipv4] Error 2
Makefile:1020: recipe for target 'net' failed
make: *** [net] Error 2



Tested on net commit
176bfb406d735655f9a69d868a7af0c3da959d51 (Tue Feb 6 16:48:40 2018 +0000)
Merge branch 'be2net-patch-set'

compiler: gcc (GCC) 7.1.1 20170620
Patch is attached.



--- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
+++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
@@ -230,17 +230,6 @@ clusterip_config_init(struct net *net, const struct 
ipt_clusterip_tgt_info *i,
        refcount_set(&c->refcount, 1);
        refcount_set(&c->entries, 1);
 
-       spin_lock_bh(&cn->lock);
-       if (__clusterip_config_find(net, ip)) {
-               spin_unlock_bh(&cn->lock);
-               kfree(c);
-
-               return ERR_PTR(-EBUSY);
-       }
-
-       list_add_rcu(&c->list, &cn->configs);
-       spin_unlock_bh(&cn->lock);
-
 #ifdef CONFIG_PROC_FS
        {
                char buffer[16];
@@ -257,20 +246,31 @@ clusterip_config_init(struct net *net, const struct 
ipt_clusterip_tgt_info *i,
        }
 #endif
 
+       spin_lock_bh(&cn->lock);
+       if (__clusterip_config_find(net, ip)) {
+               spin_unlock_bh(&cn->lock);
+               err = -EBUSY;
+               goto err_remove_pte:
+       }
+
+       list_add_rcu(&c->list, &cn->configs);
+       spin_unlock_bh(&cn->lock);
+
        c->notifier.notifier_call = clusterip_netdev_event;
        err = register_netdevice_notifier(&c->notifier);
        if (!err)
                return c;
 
+       spin_lock_bh(&cn->lock);
+       list_del_rcu(&c->list);
+       spin_unlock_bh(&cn->lock);
+
+err_remove_pte:
 #ifdef CONFIG_PROC_FS
        proc_remove(c->pde);
 err:
 #endif
-       spin_lock_bh(&cn->lock);
-       list_del_rcu(&c->list);
-       spin_unlock_bh(&cn->lock);
        kfree(c);
-
        return ERR_PTR(err);
 }