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unix: Show number of pending scm files of receive queue in fdinfo 

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.

v2: Pass correct argument to lockdep

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Kirill Tkhai 2019-12-09 13:03:46 +03:00 committed by David S. Miller
parent b4653342b1
commit 3c32da19a8
2 changed files with 56 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/net/af_unix.h
View File

@ -41,6 +41,10 @@ struct unix_skb_parms {
u32 consumed;
} __randomize_layout;
struct scm_stat {
u32 nr_fds;
};
#define UNIXCB(skb) (*(struct unix_skb_parms *)&((skb)->cb))
#define unix_state_lock(s) spin_lock(&unix_sk(s)->lock)
@ -65,6 +69,7 @@ struct unix_sock {
#define UNIX_GC_MAYBE_CYCLE 1
struct socket_wq peer_wq;
wait_queue_entry_t peer_wake;
struct scm_stat scm_stat;
};
static inline struct unix_sock *unix_sk(const struct sock *sk)

56
net/unix/af_unix.c
View File

@ -676,6 +676,16 @@ 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,
@ -701,6 +711,7 @@ 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 = {
@ -726,6 +737,7 @@ 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 = {
@ -751,6 +763,7 @@ 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 = {
@ -788,6 +801,7 @@ static struct sock *unix_create1(struct net *net, struct socket *sock, int kern)
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)
@ -1572,6 +1586,28 @@ static bool unix_skb_scm_eq(struct sk_buff *skb,
unix_secdata_eq(scm, skb);
}
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.
*/
@ -1757,7 +1793,10 @@ restart_locked:
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);
unix_state_unlock(other);
other->sk_data_ready(other);
sock_put(other);
@ -1859,7 +1898,10 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,
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);
unix_state_unlock(other);
other->sk_data_ready(other);
sent += size;
@ -2058,8 +2100,8 @@ static int unix_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
mutex_lock(&u->iolock);
skip = sk_peek_offset(sk, flags);
skb = __skb_try_recv_datagram(sk, flags, NULL, &skip, &err,
&last);
skb = __skb_try_recv_datagram(sk, flags, scm_stat_del,
&skip, &err, &last);
if (skb)
break;
@ -2353,8 +2395,12 @@ unlock:
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(&scm, skb);
}
if (unix_skb_len(skb))
break;