Unix sockets like a block box. You never know what is stored there:
there may be a file descriptor holding a mount or a block device,
or there may be whole universes with namespaces, sockets with receive
queues full of sockets etc.
The patch adds a little debug and accounts number of files (not recursive),
which is in receive queue of a unix socket. Sometimes this is useful
to determine, that socket should be investigated or which task should
be killed to put reference counter on a resourse.
Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
include/net/af_unix.h | 5 +++++
net/unix/af_unix.c | 54 +++++++++++++++++++++++++++++++++++++++++++++----
2 files changed, 55 insertions(+), 4 deletions(-)
diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index 4f975b0e6fae..33e5b5b55f4a 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -38,6 +38,10 @@ struct unix_skb_parms {
u32 consumed;
};
+struct scm_stat {
+ u32 nr_fds;
+};
+
#define UNIXCB(skb) (*(struct unix_skb_parms *)&((skb)->cb))
#define UNIXSID(skb) (&UNIXCB((skb)).secid)
@@ -64,6 +68,7 @@ struct unix_sock {
#define UNIX_GC_MAYBE_CYCLE 1
struct socket_wq peer_wq;
wait_queue_t peer_wake;
+ struct scm_stat scm_stat;
};
#define unix_sk(__sk) ((struct unix_sock *)__sk)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 5c77a0335039..8223c5bf9de1 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -664,6 +664,16 @@ static int unix_set_peek_off(struct sock *sk, int val)
return 0;
}
+static void unix_show_fdinfo(struct seq_file *m, struct socket *sock)
+{
+ struct sock *sk = sock->sk;
+ struct unix_sock *u;
+
+ if (sk) {
+ u = unix_sk(sock->sk);
+ seq_printf(m, "scm_fds: %u\n", READ_ONCE(u->scm_stat.nr_fds));
+ }
+}
static const struct proto_ops unix_stream_ops = {
.family = PF_UNIX,
@@ -686,6 +696,7 @@ static const struct proto_ops unix_stream_ops = {
.sendpage = unix_stream_sendpage,
.splice_read = unix_stream_splice_read,
.set_peek_off = unix_set_peek_off,
+ .show_fdinfo = unix_show_fdinfo,
};
static const struct proto_ops unix_dgram_ops = {
@@ -708,6 +719,7 @@ static const struct proto_ops unix_dgram_ops = {
.mmap = sock_no_mmap,
.sendpage = sock_no_sendpage,
.set_peek_off = unix_set_peek_off,
+ .show_fdinfo = unix_show_fdinfo,
};
static const struct proto_ops unix_seqpacket_ops = {
@@ -730,6 +742,7 @@ static const struct proto_ops unix_seqpacket_ops = {
.mmap = sock_no_mmap,
.sendpage = sock_no_sendpage,
.set_peek_off = unix_set_peek_off,
+ .show_fdinfo = unix_show_fdinfo,
};
static struct proto unix_proto = {
@@ -777,6 +790,7 @@ static struct sock *unix_create1(struct net *net, struct socket *sock)
mutex_init(&u->bindlock); /* single task binding lock */
init_waitqueue_head(&u->peer_wait);
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)
@@ -1619,6 +1633,28 @@ static bool unix_skb_scm_eq(struct sk_buff *skb,
gid_eq(u->gid, scm->creds.gid);
}
+static void scm_stat_add(struct sock *sk, struct sk_buff *skb)
+{
+ struct scm_fp_list *fp = UNIXCB(skb).fp;
+ struct unix_sock *u = unix_sk(sk);
+
+ lockdep_assert_held(&sk->sk_receive_queue.lock);
+
+ if (unlikely(fp && fp->count))
+ u->scm_stat.nr_fds += fp->count;
+}
+
+static void scm_stat_del(struct sock *sk, struct sk_buff *skb)
+{
+ struct scm_fp_list *fp = UNIXCB(skb).fp;
+ struct unix_sock *u = unix_sk(sk);
+
+ lockdep_assert_held(&sk->sk_receive_queue.lock);
+
+ if (unlikely(fp && fp->count))
+ u->scm_stat.nr_fds -= fp->count;
+}
+
/*
* Send AF_UNIX data.
*/
@@ -1810,7 +1846,10 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
if (sock_flag(other, SOCK_RCVTSTAMP))
__net_timestamp(skb);
maybe_add_creds(skb, sock, other);
- skb_queue_tail(&other->sk_receive_queue, skb);
+ spin_lock(&other->sk_receive_queue.lock);
+ scm_stat_add(other, skb);
+ __skb_queue_tail(&other->sk_receive_queue, skb);
+ spin_unlock(&other->sk_receive_queue.lock);
if (max_level > unix_sk(other)->recursion_level)
unix_sk(other)->recursion_level = max_level;
unix_state_unlock(other);
@@ -1920,7 +1959,10 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
goto pipe_err_free;
maybe_add_creds(skb, sock, other);
- skb_queue_tail(&other->sk_receive_queue, skb);
+ spin_lock(&other->sk_receive_queue.lock);
+ scm_stat_add(other, skb);
+ __skb_queue_tail(&other->sk_receive_queue, skb);
+ spin_unlock(&other->sk_receive_queue.lock);
if (max_level > unix_sk(other)->recursion_level)
unix_sk(other)->recursion_level = max_level;
unix_state_unlock(other);
@@ -2131,7 +2173,7 @@ static int unix_dgram_recvmsg(struct kiocb *iocb, struct socket *sock,
skip = sk_peek_offset(sk, flags);
- skb = __skb_recv_datagram(sk, flags, NULL, &peeked, &skip, &err);
+ skb = __skb_recv_datagram(sk, flags, scm_stat_del, &peeked, &skip, &err);
if (!skb) {
unix_state_lock(sk);
/* Signal EOF on disconnected non-blocking SEQPACKET socket. */
@@ -2424,8 +2466,12 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state)
sk_peek_offset_bwd(sk, chunk);
- if (UNIXCB(skb).fp)
+ if (UNIXCB(skb).fp) {
+ spin_lock(&sk->sk_receive_queue.lock);
+ scm_stat_del(sk, skb);
+ spin_unlock(&sk->sk_receive_queue.lock);
unix_detach_fds(siocb->scm, skb);
+ }
if (unix_skb_len(skb))
break;