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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: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Kuniyuki Iwashima 2021-09-28 09:42:27 +09:00 committed by David S. Miller
parent a9f5970767
commit f4bd73b5a9
1 changed files with 32 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

49
net/unix/af_unix.c
View File

@ -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();
}
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);