Patch-mainline: never (revert original patch due to kabi)
References: bsc#1179508 XSA-349 CVE-2020-29568
From: Juergen Gross <jgross@suse.com>
Date: Tue, 22 Dec 2020 10:14:27 +0100
Subject: [PATCH] xen: revert Allow watches discard events before queueing

Due to kabi changes revert original patch
"xen/xenbus: Allow watches discard events before queueing"
(commit fed1755b118147721f2c87b37b9d66e62c39b668 upstream).

The issue will be fixed differently in a followup patch.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/net/xen-netback/xenbus.c   | 4 ----
 drivers/xen/xenbus/xenbus_client.c | 1 -
 drivers/xen/xenbus/xenbus_xs.c     | 5 +----
 include/xen/xenbus.h               | 7 -------
 4 files changed, 1 insertion(+), 16 deletions(-)

diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index e46276f8e4a5..a56d3eab35dd 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -777,14 +777,12 @@ static int xen_register_credit_watch(struct xenbus_device *dev,
 		return -ENOMEM;
 	snprintf(node, maxlen, "%s/rate", dev->nodename);
 	vif->credit_watch.node = node;
-	vif->credit_watch.will_handle = NULL;
 	vif->credit_watch.callback = xen_net_rate_changed;
 	err = register_xenbus_watch(&vif->credit_watch);
 	if (err) {
 		pr_err("Failed to set watcher %s\n", vif->credit_watch.node);
 		kfree(node);
 		vif->credit_watch.node = NULL;
-		vif->credit_watch.will_handle = NULL;
 		vif->credit_watch.callback = NULL;
 	}
 	return err;
@@ -831,7 +829,6 @@ static int xen_register_mcast_ctrl_watch(struct xenbus_device *dev,
 	snprintf(node, maxlen, "%s/request-multicast-control",
 		 dev->otherend);
 	vif->mcast_ctrl_watch.node = node;
-	vif->mcast_ctrl_watch.will_handle = NULL;
 	vif->mcast_ctrl_watch.callback = xen_mcast_ctrl_changed;
 	err = register_xenbus_watch(&vif->mcast_ctrl_watch);
 	if (err) {
@@ -839,7 +836,6 @@ static int xen_register_mcast_ctrl_watch(struct xenbus_device *dev,
 		       vif->mcast_ctrl_watch.node);
 		kfree(node);
 		vif->mcast_ctrl_watch.node = NULL;
-		vif->mcast_ctrl_watch.will_handle = NULL;
 		vif->mcast_ctrl_watch.callback = NULL;
 	}
 	return err;
diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index 17602ba6d5b2..82a8866758ee 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -120,7 +120,6 @@ int xenbus_watch_path(struct xenbus_device *dev, const char *path,
 	int err;
 
 	watch->node = path;
-	watch->will_handle = NULL;
 	watch->callback = callback;
 
 	err = register_xenbus_watch(watch);
diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index 992275f811b2..e46080214955 100644
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -694,10 +694,7 @@ int xs_watch_msg(struct xs_watch_event *event)
 
 	spin_lock(&watches_lock);
 	event->handle = find_watch(event->token);
-	if (event->handle != NULL &&
-			(!event->handle->will_handle ||
-			 event->handle->will_handle(event->handle,
-				 event->path, event->token))) {
+	if (event->handle != NULL) {
 		spin_lock(&watch_events_lock);
 		list_add_tail(&event->list, &watch_events);
 		wake_up(&watch_events_waitq);
diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h
index 55f543fe0bd8..869c816d5f8c 100644
--- a/include/xen/xenbus.h
+++ b/include/xen/xenbus.h
@@ -59,13 +59,6 @@ struct xenbus_watch
 	/* Path being watched. */
 	const char *node;
 
-	/*
-	 * Called just before enqueing new event while a spinlock is held.
-	 * The event will be discarded if this callback returns false.
-	 */
-	bool (*will_handle)(struct xenbus_watch *,
-			      const char *path, const char *token);
-
 	/* Callback (executed in a process context with no locks held). */
 	void (*callback)(struct xenbus_watch *,
 			 const char *path, const char *token);
-- 
2.26.2