Re: [PATCH] tcp: fix race condition when creating child sockets from syncookies

[kernel test robot]

Hi Ricardo,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on net-next/master]
[also build test WARNING on net/master linus/master v5.9 next-20201023]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Ricardo-Dias/tcp-fix-race-condition-when-creating-child-sockets-from-syncookies/20201023-191433
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git 105faa8742437c28815b2a3eb8314ebc5fd9288c
config: arm-randconfig-r023-20201022 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 147b9497e79a98a8614b2b5eb4ba653b44f6b6f0)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        # https://github.com/0day-ci/linux/commit/35d7202175fe2c313d66daf214ea113947d78c6d
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Ricardo-Dias/tcp-fix-race-condition-when-creating-child-sockets-from-syncookies/20201023-191433
        git checkout 35d7202175fe2c313d66daf214ea113947d78c6d
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All warnings (new ones prefixed by >>):

>> net/ipv4/inet_hashtables.c:572:11: warning: variable 'dif' is uninitialized when used here [-Wuninitialized]
                                         dif, sdif))) {
                                         ^~~
   include/net/inet_hashtables.h:318:33: note: expanded from macro 'INET_MATCH'
            (((__sk)->sk_bound_dev_if == (__dif))          ||              \
                                          ^~~~~
   include/linux/compiler.h:77:40: note: expanded from macro 'likely'
   # define likely(x)      __builtin_expect(!!(x), 1)
                                               ^
   net/ipv4/inet_hashtables.c:553:15: note: initialize the variable 'dif' to silence this warning
           const int dif, sdif = sk->sk_bound_dev_if;
                        ^
                         = 0
   1 warning generated.

vim +/dif +572 net/ipv4/inet_hashtables.c

   539	
   540	/* Inserts a socket into ehash if no existing socket exists for the same
   541	 * quadruple (saddr, sport, daddr, dport).
   542	 * If there is an existing socket, returns that socket, otherwise returns NULL.
   543	 */
   544	struct sock *inet_ehash_insert_chk_dup(struct sock *sk)
   545	{
   546		struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
   547		struct hlist_nulls_head *list;
   548		struct inet_ehash_bucket *head;
   549		const struct hlist_nulls_node *node;
   550		struct sock *esk;
   551		spinlock_t *lock; /* protects hashinfo socket entry */
   552		struct net *net = sock_net(sk);
   553		const int dif, sdif = sk->sk_bound_dev_if;
   554	
   555		INET_ADDR_COOKIE(acookie, sk->sk_daddr, sk->sk_rcv_saddr);
   556		const __portpair ports = INET_COMBINED_PORTS(sk->sk_dport, sk->sk_num);
   557	
   558		WARN_ON_ONCE(!sk_unhashed(sk));
   559	
   560		sk->sk_hash = sk_ehashfn(sk);
   561		head = inet_ehash_bucket(hashinfo, sk->sk_hash);
   562		list = &head->chain;
   563		lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
   564	
   565		spin_lock(lock);
   566	begin:
   567		sk_nulls_for_each_rcu(esk, node, list) {
   568			if (esk->sk_hash != sk->sk_hash)
   569				continue;
   570			if (likely(INET_MATCH(esk, net, acookie,
   571					      sk->sk_daddr, sk->sk_rcv_saddr, ports,
 > 572					      dif, sdif))) {
   573				if (unlikely(!refcount_inc_not_zero(&esk->sk_refcnt)))
   574					goto out;
   575				if (unlikely(!INET_MATCH(esk, net, acookie,
   576							 sk->sk_daddr,
   577							 sk->sk_rcv_saddr, ports,
   578							 dif, sdif))) {
   579					sock_gen_put(esk);
   580					goto begin;
   581				}
   582				goto found;
   583			}
   584		}
   585	out:
   586		esk = NULL;
   587		__sk_nulls_add_node_rcu(sk, list);
   588	found:
   589		spin_unlock(lock);
   590		if (esk) {
   591			percpu_counter_inc(sk->sk_prot->orphan_count);
   592			inet_sk_set_state(sk, TCP_CLOSE);
   593			sock_set_flag(sk, SOCK_DEAD);
   594			inet_csk_destroy_sock(sk);
   595		}
   596		return esk;
   597	}
   598	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx

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