[PATCH net v3] net: x25: fix one potential use-after-free issue

[linzhang]

The function x25_init is not properly unregister related resources
on error handler.It is will result in kernel oops if x25_init init
failed, so add properly unregister call on error handler.

Also, i adjust the coding style and make x25_register_sysctl properly
return failure.

Signed-off-by: linzhang <xiaolou4...@gmail.com>
---

changelog:

v1 -> v2:
        * make x25_register_sysctl properly return failure

v2 -> v3:
        * keep the same lables as v1
        * fix missing semicolon

---
 include/net/x25.h        |  4 ++--
 net/x25/af_x25.c         | 24 ++++++++++++++++--------
 net/x25/sysctl_net_x25.c |  5 ++++-
 3 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/include/net/x25.h b/include/net/x25.h
index c383aa4..6d30a01 100644
--- a/include/net/x25.h
+++ b/include/net/x25.h
@@ -298,10 +298,10 @@ int x25_decode(struct sock *, struct sk_buff *, int *, 
int *, int *, int *,
 
 /* sysctl_net_x25.c */
 #ifdef CONFIG_SYSCTL
-void x25_register_sysctl(void);
+int x25_register_sysctl(void);
 void x25_unregister_sysctl(void);
 #else
-static inline void x25_register_sysctl(void) {};
+static inline int x25_register_sysctl(void) { return 0; };
 static inline void x25_unregister_sysctl(void) {};
 #endif /* CONFIG_SYSCTL */
 
diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index 8b911c2..5a1a98d 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -1791,32 +1791,40 @@ void x25_kill_by_neigh(struct x25_neigh *nb)
 
 static int __init x25_init(void)
 {
-       int rc = proto_register(&x25_proto, 0);
+       int rc;
 
-       if (rc != 0)
+       rc = proto_register(&x25_proto, 0);
+       if (rc)
                goto out;
 
        rc = sock_register(&x25_family_ops);
-       if (rc != 0)
+       if (rc)
                goto out_proto;
 
        dev_add_pack(&x25_packet_type);
 
        rc = register_netdevice_notifier(&x25_dev_notifier);
-       if (rc != 0)
+       if (rc)
                goto out_sock;
 
-       pr_info("Linux Version 0.2\n");
+       rc = x25_register_sysctl();
+       if (rc)
+               goto out_dev;
 
-       x25_register_sysctl();
        rc = x25_proc_init();
-       if (rc != 0)
-               goto out_dev;
+       if (rc)
+               goto out_sysctl;
+
+       pr_info("Linux Version 0.2\n");
+
 out:
        return rc;
+out_sysctl:
+       x25_unregister_sysctl();
 out_dev:
        unregister_netdevice_notifier(&x25_dev_notifier);
 out_sock:
+       dev_remove_pack(&x25_packet_type);
        sock_unregister(AF_X25);
 out_proto:
        proto_unregister(&x25_proto);
diff --git a/net/x25/sysctl_net_x25.c b/net/x25/sysctl_net_x25.c
index a06dfe1..ba078c8 100644
--- a/net/x25/sysctl_net_x25.c
+++ b/net/x25/sysctl_net_x25.c
@@ -73,9 +73,12 @@
        { },
 };
 
-void __init x25_register_sysctl(void)
+int __init x25_register_sysctl(void)
 {
        x25_table_header = register_net_sysctl(&init_net, "net/x25", x25_table);
+       if (!x25_table_header)
+               return -ENOMEM;
+       return 0;
 }
 
 void x25_unregister_sysctl(void)
-- 
1.8.3.1