[PATCH] sock: fix potential memory leak in proto_register()

[zhanglin]

If protocols registered exceeded PROTO_INUSE_NR, prot will be
added to proto_list, but no available bit left for prot in
proto_inuse_idx.

Signed-off-by: zhanglin <zhang.li...@zte.com.cn>
---
 net/core/sock.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index bc3512f230a3..25388d429f6a 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -3139,16 +3139,17 @@ static __init int net_inuse_init(void)
 
 core_initcall(net_inuse_init);
 
-static void assign_proto_idx(struct proto *prot)
+static int assign_proto_idx(struct proto *prot)
 {
        prot->inuse_idx = find_first_zero_bit(proto_inuse_idx, PROTO_INUSE_NR);
 
        if (unlikely(prot->inuse_idx == PROTO_INUSE_NR - 1)) {
                pr_err("PROTO_INUSE_NR exhausted\n");
-               return;
+               return -ENOSPC;
        }
 
        set_bit(prot->inuse_idx, proto_inuse_idx);
+       return 0;
 }
 
 static void release_proto_idx(struct proto *prot)
@@ -3243,18 +3244,24 @@ int proto_register(struct proto *prot, int alloc_slab)
        }
 
        mutex_lock(&proto_list_mutex);
+       if (assign_proto_idx(prot)) {
+               mutex_unlock(&proto_list_mutex);
+               goto out_free_timewait_sock_slab_name;
+       }
        list_add(&prot->node, &proto_list);
-       assign_proto_idx(prot);
        mutex_unlock(&proto_list_mutex);
        return 0;
 
 out_free_timewait_sock_slab_name:
-       kfree(prot->twsk_prot->twsk_slab_name);
+       if (alloc_slab && prot->twsk_prot)
+               kfree(prot->twsk_prot->twsk_slab_name);
 out_free_request_sock_slab:
-       req_prot_cleanup(prot->rsk_prot);
+       if (alloc_slab) {
+               req_prot_cleanup(prot->rsk_prot);
 
-       kmem_cache_destroy(prot->slab);
-       prot->slab = NULL;
+               kmem_cache_destroy(prot->slab);
+               prot->slab = NULL;
+       }
 out:
        return -ENOBUFS;
 }
-- 
2.17.1