2 files changed, 40 insertions, 6 deletions

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 0b39b2451ea5..b4cfe207a6ac 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1343,9 +1343,25 @@ static void unix_destruct_scm(struct sk_buff *skb)
         sock_wfree(skb);
 }
 
+#define MAX_RECURSION_LEVEL 4
+
 static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
 {
         int i;
+        unsigned char max_level = 0;
+        int unix_sock_count = 0;
+
+        for (i = scm->fp->count - 1; i >= 0; i--) {
+                struct sock *sk = unix_get_socket(scm->fp->fp[i]);
+
+                if (sk) {
+                        unix_sock_count++;
+                        max_level = max(max_level,
+                                        unix_sk(sk)->recursion_level);
+                }
+        }
+        if (unlikely(max_level > MAX_RECURSION_LEVEL))
+                return -ETOOMANYREFS;
 
         /*
          * Need to duplicate file references for the sake of garbage
@@ -1356,9 +1372,11 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
         if (!UNIXCB(skb).fp)
                 return -ENOMEM;
 
-        for (i = scm->fp->count-1; i >= 0; i--)
-                unix_inflight(scm->fp->fp[i]);
-        return 0;
+        if (unix_sock_count) {
+                for (i = scm->fp->count - 1; i >= 0; i--)
+                        unix_inflight(scm->fp->fp[i]);
+        }
+        return max_level;
 }
 
 static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb, bool send_fds)
@@ -1393,6 +1411,7 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
         struct sk_buff *skb;
         long timeo;
         struct scm_cookie tmp_scm;
+        int max_level;
 
         if (NULL == siocb->scm)
                 siocb->scm = &tmp_scm;
@@ -1431,8 +1450,9 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
                 goto out;
 
         err = unix_scm_to_skb(siocb->scm, skb, true);
-        if (err)
+        if (err < 0)
                 goto out_free;
+        max_level = err + 1;
         unix_get_secdata(siocb->scm, skb);
 
         skb_reset_transport_header(skb);
@@ -1512,6 +1532,8 @@ restart:
         }
 
         skb_queue_tail(&other->sk_receive_queue, skb);
+        if (max_level > unix_sk(other)->recursion_level)
+                unix_sk(other)->recursion_level = max_level;
         unix_state_unlock(other);
         other->sk_data_ready(other, len);
         sock_put(other);
@@ -1542,6 +1564,7 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
         int sent = 0;
         struct scm_cookie tmp_scm;
         bool fds_sent = false;
+        int max_level;
 
         if (NULL == siocb->scm)
                 siocb->scm = &tmp_scm;
@@ -1605,10 +1628,11 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
 
                 /* Only send the fds in the first buffer */
                 err = unix_scm_to_skb(siocb->scm, skb, !fds_sent);
-                if (err) {
+                if (err < 0) {
                         kfree_skb(skb);
                         goto out_err;
                 }
+                max_level = err + 1;
                 fds_sent = true;
 
                 err = memcpy_fromiovec(skb_put(skb, size), msg->msg_iov, size);
@@ -1624,6 +1648,8 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
                         goto pipe_err_free;
 
                 skb_queue_tail(&other->sk_receive_queue, skb);
+                if (max_level > unix_sk(other)->recursion_level)
+                        unix_sk(other)->recursion_level = max_level;
                 unix_state_unlock(other);
                 other->sk_data_ready(other, size);
                 sent += size;
@@ -1840,6 +1866,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
                 unix_state_lock(sk);
                 skb = skb_dequeue(&sk->sk_receive_queue);
                 if (skb == NULL) {
+                        unix_sk(sk)->recursion_level = 0;
                         if (copied >= target)
                                 goto unlock;
 
diff --git a/net/unix/garbage.c b/net/unix/garbage.c
index c8df6fda0b1f..f89f83bf828e 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -96,7 +96,7 @@ static DECLARE_WAIT_QUEUE_HEAD(unix_gc_wait);
 unsigned int unix_tot_inflight;
 
 
-static struct sock *unix_get_socket(struct file *filp)
+struct sock *unix_get_socket(struct file *filp)
 {
         struct sock *u_sock = NULL;
         struct inode *inode = filp->f_path.dentry->d_inode;
@@ -259,9 +259,16 @@ static void inc_inflight_move_tail(struct unix_sock *u)
 }
 
 static bool gc_in_progress = false;
+#define UNIX_INFLIGHT_TRIGGER_GC 16000
 
 void wait_for_unix_gc(void)
 {
+        /*
+         * If number of inflight sockets is insane,
+         * force a garbage collect right now.
+         */
+        if (unix_tot_inflight > UNIX_INFLIGHT_TRIGGER_GC && !gc_in_progress)
+                unix_gc();
         wait_event(unix_gc_wait, gc_in_progress == false);
 }