Commit f4bd73b5 authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by David S. Miller
Browse files

af_unix: Return errno instead of NULL in unix_create1(). 

unix_create1() returns NULL on error, and the callers assume that it never
fails for reasons other than out of memory.  So, the callers always return
-ENOMEM when unix_create1() fails.

However, it also returns NULL when the number of af_unix sockets exceeds
twice the limit controlled by sysctl: fs.file-max.  In this case, the
callers should return -ENFILE like alloc_empty_file().

This patch changes unix_create1() to return the correct error value instead
of NULL on error.

Out of curiosity, the assumption has been wrong since 1999 due to this
change introduced in 2.2.4 [0].

  diff -u --recursive --new-file v2.2.3/linux/net/unix/af_unix.c linux/net/unix/af_unix.c
  --- v2.2.3/linux/net/unix/af_unix.c	Tue Jan 19 11:32:53 1999
  +++ linux/net/unix/af_unix.c	Sun Mar 21 07:22:00 1999
  @@ -388,6 +413,9 @@
   {
   	struct sock *sk;

  +	if (atomic_read(&unix_nr_socks) >= 2*max_files)
  +		return NULL;
  +
   	MOD_INC_USE_COUNT;
   	sk = sk_alloc(PF_UNIX, GFP_KERNEL, 1);
   	if (!sk) {

[0]: https://cdn.kernel.org/pub/linux/kernel/v2.2/patch-2.2.4.gz



Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.co.jp>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a9f59707

net/unix/af_unix.c

+32 −17
Original line number Diff line number Diff line
@@ -828,20 +828,25 @@ struct proto unix_stream_proto = { 


static struct sock *unix_create1(struct net *net, struct socket *sock, int kern, int type)

{

	struct sock *sk = NULL;

	struct unix_sock *u;

	struct sock *sk;

	int err;



	atomic_long_inc(&unix_nr_socks);

	if (atomic_long_read(&unix_nr_socks) > 2 * get_max_files())

		goto out;

	if (atomic_long_read(&unix_nr_socks) > 2 * get_max_files()) {

		err = -ENFILE;

		goto err;

	}



	if (type == SOCK_STREAM)

		sk = sk_alloc(net, PF_UNIX, GFP_KERNEL, &unix_stream_proto, kern);

	else /*dgram and  seqpacket */

		sk = sk_alloc(net, PF_UNIX, GFP_KERNEL, &unix_dgram_proto, kern);



	if (!sk)

		goto out;

	if (!sk) {

		err = -ENOMEM;

		goto err;

	}



	sock_init_data(sock, sk);
@@ -861,20 +866,23 @@ static struct sock *unix_create1(struct net *net, struct socket *sock, int kern, 
	init_waitqueue_func_entry(&u->peer_wake, unix_dgram_peer_wake_relay);

	memset(&u->scm_stat, 0, sizeof(struct scm_stat));

	unix_insert_socket(unix_sockets_unbound(sk), sk);

out:

	if (sk == NULL)

		atomic_long_dec(&unix_nr_socks);

	else {



	local_bh_disable();

	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);

	local_bh_enable();

	}



	return sk;



err:

	atomic_long_dec(&unix_nr_socks);

	return ERR_PTR(err);

}



static int unix_create(struct net *net, struct socket *sock, int protocol,

		       int kern)

{

	struct sock *sk;



	if (protocol && protocol != PF_UNIX)

		return -EPROTONOSUPPORT;
@@ -901,7 +909,11 @@ static int unix_create(struct net *net, struct socket *sock, int protocol, 
		return -ESOCKTNOSUPPORT;

	}



	return unix_create1(net, sock, kern, sock->type) ? 0 : -ENOMEM;

	sk = unix_create1(net, sock, kern, sock->type);

	if (IS_ERR(sk))

		return PTR_ERR(sk);



	return 0;

}



static int unix_release(struct socket *sock)
@@ -1314,12 +1326,15 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr, 
	   we will have to recheck all again in any case.

	 */



	err = -ENOMEM;



	/* create new sock for complete connection */

	newsk = unix_create1(sock_net(sk), NULL, 0, sock->type);

	if (newsk == NULL)

	if (IS_ERR(newsk)) {

		err = PTR_ERR(newsk);

		newsk = NULL;

		goto out;

	}



	err = -ENOMEM;



	/* Allocate skb for sending to listening sock */

	skb = sock_wmalloc(newsk, 1, 0, GFP_KERNEL);