1 files changed, 312 insertions, 0 deletions
diff --git a/net/unix/garbage.c b/net/unix/garbage.c
new file mode 100644
index 00000000000..4bd95c8f593
--- /dev/null
+++ b/net/unix/garbage.c
@@ -0,0 +1,312 @@
+/*
+ * NET3:	Garbage Collector For AF_UNIX sockets
+ *
+ * Garbage Collector:
+ *	Copyright (C) Barak A. Pearlmutter.
+ *	Released under the GPL version 2 or later.
+ *
+ * Chopped about by Alan Cox 22/3/96 to make it fit the AF_UNIX socket problem.
+ * If it doesn't work blame me, it worked when Barak sent it.
+ *
+ * Assumptions:
+ *
+ *  - object w/ a bit
+ *  - free list
+ *
+ * Current optimizations:
+ *
+ *  - explicit stack instead of recursion
+ *  - tail recurse on first born instead of immediate push/pop
+ *  - we gather the stuff that should not be killed into tree
+ *    and stack is just a path from root to the current pointer.
+ *
+ *  Future optimizations:
+ *
+ *  - don't just push entire root set; process in place
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ *
+ *  Fixes:
+ *	Alan Cox	07 Sept	1997	Vmalloc internal stack as needed.
+ *					Cope with changing max_files.
+ *	Al Viro		11 Oct 1998
+ *		Graph may have cycles. That is, we can send the descriptor
+ *		of foo to bar and vice versa. Current code chokes on that.
+ *		Fix: move SCM_RIGHTS ones into the separate list and then
+ *		skb_free() them all instead of doing explicit fput's.
+ *		Another problem: since fput() may block somebody may
+ *		create a new unix_socket when we are in the middle of sweep
+ *		phase. Fix: revert the logic wrt MARKED. Mark everything
+ *		upon the beginning and unmark non-junk ones.
+ *
+ *		[12 Oct 1998] AAARGH! New code purges all SCM_RIGHTS
+ *		sent to connect()'ed but still not accept()'ed sockets.
+ *		Fixed. Old code had slightly different problem here:
+ *		extra fput() in situation when we passed the descriptor via
+ *		such socket and closed it (descriptor). That would happen on
+ *		each unix_gc() until the accept(). Since the struct file in
+ *		question would go to the free list and might be reused...
+ *		That might be the reason of random oopses on filp_close()
+ *		in unrelated processes.
+ *
+ *	AV		28 Feb 1999
+ *		Kill the explicit allocation of stack. Now we keep the tree
+ *		with root in dummy + pointer (gc_current) to one of the nodes.
+ *		Stack is represented as path from gc_current to dummy. Unmark
+ *		now means "add to tree". Push == "make it a son of gc_current".
+ *		Pop == "move gc_current to parent". We keep only pointers to
+ *		parents (->gc_tree).
+ *	AV		1 Mar 1999
+ *		Damn. Added missing check for ->dead in listen queues scanning.
+ *
+ */
+ 
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/string.h>
+#include <linux/socket.h>
+#include <linux/un.h>
+#include <linux/net.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/skbuff.h>
+#include <linux/netdevice.h>
+#include <linux/file.h>
+#include <linux/proc_fs.h>
+#include <linux/tcp.h>
+
+#include <net/sock.h>
+#include <net/af_unix.h>
+#include <net/scm.h>
+
+/* Internal data structures and random procedures: */
+
+#define GC_HEAD		((struct sock *)(-1))
+#define GC_ORPHAN	((struct sock *)(-3))
+
+static struct sock *gc_current = GC_HEAD; /* stack of objects to mark */
+
+atomic_t unix_tot_inflight = ATOMIC_INIT(0);
+
+
+static struct sock *unix_get_socket(struct file *filp)
+{
+	struct sock *u_sock = NULL;
+	struct inode *inode = filp->f_dentry->d_inode;
+
+	/*
+	 *	Socket ?
+	 */
+	if (S_ISSOCK(inode->i_mode)) {
+		struct socket * sock = SOCKET_I(inode);
+		struct sock * s = sock->sk;
+
+		/*
+		 *	PF_UNIX ?
+		 */
+		if (s && sock->ops && sock->ops->family == PF_UNIX)
+			u_sock = s;
+	}
+	return u_sock;
+}
+
+/*
+ *	Keep the number of times in flight count for the file
+ *	descriptor if it is for an AF_UNIX socket.
+ */
+ 
+void unix_inflight(struct file *fp)
+{
+	struct sock *s = unix_get_socket(fp);
+	if(s) {
+		atomic_inc(&unix_sk(s)->inflight);
+		atomic_inc(&unix_tot_inflight);
+	}
+}
+
+void unix_notinflight(struct file *fp)
+{
+	struct sock *s = unix_get_socket(fp);
+	if(s) {
+		atomic_dec(&unix_sk(s)->inflight);
+		atomic_dec(&unix_tot_inflight);
+	}
+}
+
+
+/*
+ *	Garbage Collector Support Functions
+ */
+
+static inline struct sock *pop_stack(void)
+{
+	struct sock *p = gc_current;
+	gc_current = unix_sk(p)->gc_tree;
+	return p;
+}
+
+static inline int empty_stack(void)
+{
+	return gc_current == GC_HEAD;
+}
+
+static void maybe_unmark_and_push(struct sock *x)
+{
+	struct unix_sock *u = unix_sk(x);
+
+	if (u->gc_tree != GC_ORPHAN)
+		return;
+	sock_hold(x);
+	u->gc_tree = gc_current;
+	gc_current = x;
+}
+
+
+/* The external entry point: unix_gc() */
+
+void unix_gc(void)
+{
+	static DECLARE_MUTEX(unix_gc_sem);
+	int i;
+	struct sock *s;
+	struct sk_buff_head hitlist;
+	struct sk_buff *skb;
+
+	/*
+	 *	Avoid a recursive GC.
+	 */
+
+	if (down_trylock(&unix_gc_sem))
+		return;
+
+	read_lock(&unix_table_lock);
+
+	forall_unix_sockets(i, s)
+	{
+		unix_sk(s)->gc_tree = GC_ORPHAN;
+	}
+	/*
+	 *	Everything is now marked 
+	 */
+
+	/* Invariant to be maintained:
+		- everything unmarked is either:
+		-- (a) on the stack, or
+		-- (b) has all of its children unmarked
+		- everything on the stack is always unmarked
+		- nothing is ever pushed onto the stack twice, because:
+		-- nothing previously unmarked is ever pushed on the stack
+	 */
+
+	/*
+	 *	Push root set
+	 */
+
+	forall_unix_sockets(i, s)
+	{
+		int open_count = 0;
+
+		/*
+		 *	If all instances of the descriptor are not
+		 *	in flight we are in use.
+		 *
+		 *	Special case: when socket s is embrion, it may be
+		 *	hashed but still not in queue of listening socket.
+		 *	In this case (see unix_create1()) we set artificial
+		 *	negative inflight counter to close race window.
+		 *	It is trick of course and dirty one.
+		 */
+		if (s->sk_socket && s->sk_socket->file)
+			open_count = file_count(s->sk_socket->file);
+		if (open_count > atomic_read(&unix_sk(s)->inflight))
+			maybe_unmark_and_push(s);
+	}
+
+	/*
+	 *	Mark phase 
+	 */
+
+	while (!empty_stack())
+	{
+		struct sock *x = pop_stack();
+		struct sock *sk;
+
+		spin_lock(&x->sk_receive_queue.lock);
+		skb = skb_peek(&x->sk_receive_queue);
+		
+		/*
+		 *	Loop through all but first born 
+		 */
+		
+		while (skb && skb != (struct sk_buff *)&x->sk_receive_queue) {
+			/*
+			 *	Do we have file descriptors ?
+			 */
+			if(UNIXCB(skb).fp)
+			{
+				/*
+				 *	Process the descriptors of this socket
+				 */
+				int nfd=UNIXCB(skb).fp->count;
+				struct file **fp = UNIXCB(skb).fp->fp;
+				while(nfd--)
+				{
+					/*
+					 *	Get the socket the fd matches if
+					 *	it indeed does so
+					 */
+					if((sk=unix_get_socket(*fp++))!=NULL)
+					{
+						maybe_unmark_and_push(sk);
+					}
+				}
+			}
+			/* We have to scan not-yet-accepted ones too */
+			if (x->sk_state == TCP_LISTEN)
+				maybe_unmark_and_push(skb->sk);
+			skb=skb->next;
+		}
+		spin_unlock(&x->sk_receive_queue.lock);
+		sock_put(x);
+	}
+
+	skb_queue_head_init(&hitlist);
+
+	forall_unix_sockets(i, s)
+	{
+		struct unix_sock *u = unix_sk(s);
+
+		if (u->gc_tree == GC_ORPHAN) {
+			struct sk_buff *nextsk;
+
+			spin_lock(&s->sk_receive_queue.lock);
+			skb = skb_peek(&s->sk_receive_queue);
+			while (skb &&
+			       skb != (struct sk_buff *)&s->sk_receive_queue) {
+				nextsk=skb->next;
+				/*
+				 *	Do we have file descriptors ?
+				 */
+				if(UNIXCB(skb).fp)
+				{
+					__skb_unlink(skb, skb->list);
+					__skb_queue_tail(&hitlist,skb);
+				}
+				skb=nextsk;
+			}
+			spin_unlock(&s->sk_receive_queue.lock);
+		}
+		u->gc_tree = GC_ORPHAN;
+	}
+	read_unlock(&unix_table_lock);
+
+	/*
+	 *	Here we are. Hitlist is filled. Die.
+	 */
+
+	__skb_queue_purge(&hitlist);
+	up(&unix_gc_sem);
+}