connector: Delete buggy notification code.

On Tue, Feb 02, 2010 at 02:57:14PM -0800, Greg KH (gregkh@suse.de) wrote:
> > There are at least two ways to fix it: using a big cannon and a small
> > one. The former way is to disable notification registration, since it is
> > not used by anyone at all. Second way is to check whether calling
> > process is root and its destination group is -1 (kind of priveledged
> > one) before command is dispatched to workqueue.
> 
> Well if no one is using it, removing it makes the most sense, right?
> 
> No objection from me, care to make up a patch either way for this?

Getting it is not used, let's drop support for notifications about
(un)registered events from connector.
Another option was to check credentials on receiving, but we can always
restore it without bugs if needed, but genetlink has a wider code base
and none complained, that userspace can not get notification when some
other clients were (un)registered.

Kudos for Sebastian Krahmer <krahmer@suse.de>, who found a bug in the
code.

Signed-off-by: Evgeniy Polyakov <zbr@ioremap.net>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/connector/connector.c

@@ -36,17 +36,6 @@ MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
 MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");
 
-static u32 cn_idx = CN_IDX_CONNECTOR;
-static u32 cn_val = CN_VAL_CONNECTOR;
-
-module_param(cn_idx, uint, 0);
-module_param(cn_val, uint, 0);
-MODULE_PARM_DESC(cn_idx, "Connector's main device idx.");
-MODULE_PARM_DESC(cn_val, "Connector's main device val.");
-
-static DEFINE_MUTEX(notify_lock);
-static LIST_HEAD(notify_list);
-
 static struct cn_dev cdev;
 
 static int cn_already_initialized;
@@ -209,54 +198,6 @@ static void cn_rx_skb(struct sk_buff *__skb)
 	}
 }
 
-/*
- * Notification routing.
- *
- * Gets id and checks if there are notification request for it's idx
- * and val.  If there are such requests notify the listeners with the
- * given notify event.
- *
- */
-static void cn_notify(struct cb_id *id, u32 notify_event)
-{
-	struct cn_ctl_entry *ent;
-
-	mutex_lock(&notify_lock);
-	list_for_each_entry(ent, &notify_list, notify_entry) {
-		int i;
-		struct cn_notify_req *req;
-		struct cn_ctl_msg *ctl = ent->msg;
-		int idx_found, val_found;
-
-		idx_found = val_found = 0;
-
-		req = (struct cn_notify_req *)ctl->data;
-		for (i = 0; i < ctl->idx_notify_num; ++i, ++req) {
-			if (id->idx >= req->first &&
-					id->idx < req->first + req->range) {
-				idx_found = 1;
-				break;
-			}
-		}
-
-		for (i = 0; i < ctl->val_notify_num; ++i, ++req) {
-			if (id->val >= req->first &&
-					id->val < req->first + req->range) {
-				val_found = 1;
-				break;
-			}
-		}
-
-		if (idx_found && val_found) {
-			struct cn_msg m = { .ack = notify_event, };
-
-			memcpy(&m.id, id, sizeof(m.id));
-			cn_netlink_send(&m, ctl->group, GFP_KERNEL);
-		}
-	}
-	mutex_unlock(&notify_lock);
-}
-
 /*
  * Callback add routing - adds callback with given ID and name.
  * If there is registered callback with the same ID it will not be added.
@@ -276,8 +217,6 @@ int cn_add_callback(struct cb_id *id, char *name,
 	if (err)
 		return err;
 
-	cn_notify(id, 0);
-
 	return 0;
 }
 EXPORT_SYMBOL_GPL(cn_add_callback);
@@ -295,111 +234,9 @@ void cn_del_callback(struct cb_id *id)
 	struct cn_dev *dev = &cdev;
 
 	cn_queue_del_callback(dev->cbdev, id);
-	cn_notify(id, 1);
 }
 EXPORT_SYMBOL_GPL(cn_del_callback);
 
-/*
- * Checks two connector's control messages to be the same.
- * Returns 1 if they are the same or if the first one is corrupted.
- */
-static int cn_ctl_msg_equals(struct cn_ctl_msg *m1, struct cn_ctl_msg *m2)
-{
-	int i;
-	struct cn_notify_req *req1, *req2;
-
-	if (m1->idx_notify_num != m2->idx_notify_num)
-		return 0;
-
-	if (m1->val_notify_num != m2->val_notify_num)
-		return 0;
-
-	if (m1->len != m2->len)
-		return 0;
-
-	if ((m1->idx_notify_num + m1->val_notify_num) * sizeof(*req1) !=
-	    m1->len)
-		return 1;
-
-	req1 = (struct cn_notify_req *)m1->data;
-	req2 = (struct cn_notify_req *)m2->data;
-
-	for (i = 0; i < m1->idx_notify_num; ++i) {
-		if (req1->first != req2->first || req1->range != req2->range)
-			return 0;
-		req1++;
-		req2++;
-	}
-
-	for (i = 0; i < m1->val_notify_num; ++i) {
-		if (req1->first != req2->first || req1->range != req2->range)
-			return 0;
-		req1++;
-		req2++;
-	}
-
-	return 1;
-}
-
-/*
- * Main connector device's callback.
- *
- * Used for notification of a request's processing.
- */
-static void cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
-{
-	struct cn_ctl_msg *ctl;
-	struct cn_ctl_entry *ent;
-	u32 size;
-
-	if (msg->len < sizeof(*ctl))
-		return;
-
-	ctl = (struct cn_ctl_msg *)msg->data;
-
-	size = (sizeof(*ctl) + ((ctl->idx_notify_num +
-				 ctl->val_notify_num) *
-				sizeof(struct cn_notify_req)));
-
-	if (msg->len != size)
-		return;
-
-	if (ctl->len + sizeof(*ctl) != msg->len)
-		return;
-
-	/*
-	 * Remove notification.
-	 */
-	if (ctl->group == 0) {
-		struct cn_ctl_entry *n;
-
-		mutex_lock(&notify_lock);
-		list_for_each_entry_safe(ent, n, &notify_list, notify_entry) {
-			if (cn_ctl_msg_equals(ent->msg, ctl)) {
-				list_del(&ent->notify_entry);
-				kfree(ent);
-			}
-		}
-		mutex_unlock(&notify_lock);
-
-		return;
-	}
-
-	size += sizeof(*ent);
-
-	ent = kzalloc(size, GFP_KERNEL);
-	if (!ent)
-		return;
-
-	ent->msg = (struct cn_ctl_msg *)(ent + 1);
-
-	memcpy(ent->msg, ctl, size - sizeof(*ent));
-
-	mutex_lock(&notify_lock);
-	list_add(&ent->notify_entry, &notify_list);
-	mutex_unlock(&notify_lock);
-}
-
 static int cn_proc_show(struct seq_file *m, void *v)
 {
 	struct cn_queue_dev *dev = cdev.cbdev;
@@ -437,11 +274,8 @@ static const struct file_operations cn_file_ops = {
 static int __devinit cn_init(void)
 {
 	struct cn_dev *dev = &cdev;
-	int err;
 
 	dev->input = cn_rx_skb;
-	dev->id.idx = cn_idx;
-	dev->id.val = cn_val;
 
 	dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR,
 					 CN_NETLINK_USERS + 0xf,
@@ -457,14 +291,6 @@ static int __devinit cn_init(void)
 
 	cn_already_initialized = 1;
 
-	err = cn_add_callback(&dev->id, "connector", &cn_callback);
-	if (err) {
-		cn_already_initialized = 0;
-		cn_queue_free_dev(dev->cbdev);
-		netlink_kernel_release(dev->nls);
-		return -EINVAL;
-	}
-
 	proc_net_fops_create(&init_net, "connector", S_IRUGO, &cn_file_ops);
 
 	return 0;
@@ -478,7 +304,6 @@ static void __devexit cn_fini(void)
 
 	proc_net_remove(&init_net, "connector");
 
-	cn_del_callback(&dev->id);
 	cn_queue_free_dev(dev->cbdev);
 	netlink_kernel_release(dev->nls);
 }

include/linux/connector.h

@@ -24,9 +24,6 @@
 
 #include <linux/types.h>
 
-#define CN_IDX_CONNECTOR		0xffffffff
-#define CN_VAL_CONNECTOR		0xffffffff
-
 /*
  * Process Events connector unique ids -- used for message routing
  */
@@ -75,30 +72,6 @@ struct cn_msg {
 	__u8 data[0];
 };
 
-/*
- * Notify structure - requests notification about
- * registering/unregistering idx/val in range [first, first+range].
- */
-struct cn_notify_req {
-	__u32 first;
-	__u32 range;
-};
-
-/*
- * Main notification control message
- * *_notify_num 	- number of appropriate cn_notify_req structures after 
- *				this struct.
- * group 		- notification receiver's idx.
- * len 			- total length of the attached data.
- */
-struct cn_ctl_msg {
-	__u32 idx_notify_num;
-	__u32 val_notify_num;
-	__u32 group;
-	__u32 len;
-	__u8 data[0];
-};
-
 #ifdef __KERNEL__
 
 #include <asm/atomic.h>
@@ -151,11 +124,6 @@ struct cn_callback_entry {
 	u32 seq, group;
 };
 
-struct cn_ctl_entry {
-	struct list_head notify_entry;
-	struct cn_ctl_msg *msg;
-};
-
 struct cn_dev {
 	struct cb_id id;