Patch "ax25: Use kernel universal linked list to implement ax25_dev_list" has been added to the 6.6-stable tree

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This is a note to let you know that I've just added the patch titled

    ax25: Use kernel universal linked list to implement ax25_dev_list

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ax25-use-kernel-universal-linked-list-to-implement-a.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 7bfd826f87b78462a5764d0d3b030a4ee40673f9
Author: Duoming Zhou <duoming@xxxxxxxxxx>
Date:   Thu May 9 17:36:33 2024 +0800

    ax25: Use kernel universal linked list to implement ax25_dev_list
    
    [ Upstream commit a7d6e36b9ad052926ba2ecba3a59d8bb67dabcb4 ]
    
    The origin ax25_dev_list implements its own single linked list,
    which is complicated and error-prone. For example, when deleting
    the node of ax25_dev_list in ax25_dev_device_down(), we have to
    operate on the head node and other nodes separately.
    
    This patch uses kernel universal linked list to replace original
    ax25_dev_list, which make the operation of ax25_dev_list easier.
    
    We should do "dev->ax25_ptr = ax25_dev;" and "dev->ax25_ptr = NULL;"
    while holding the spinlock, otherwise the ax25_dev_device_up() and
    ax25_dev_device_down() could race.
    
    Suggested-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
    Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>
    Reviewed-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/85bba3af651ca0e1a519da8d0d715b949891171c.1715247018.git.duoming@xxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Stable-dep-of: b505e0319852 ("ax25: Fix reference count leak issues of ax25_dev")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/net/ax25.h b/include/net/ax25.h
index 0d939e5aee4ec..c2a85fd3f5ea4 100644
--- a/include/net/ax25.h
+++ b/include/net/ax25.h
@@ -216,7 +216,7 @@ typedef struct {
 struct ctl_table;
 
 typedef struct ax25_dev {
-	struct ax25_dev		*next;
+	struct list_head	list;
 
 	struct net_device	*dev;
 	netdevice_tracker	dev_tracker;
@@ -330,7 +330,6 @@ int ax25_addr_size(const ax25_digi *);
 void ax25_digi_invert(const ax25_digi *, ax25_digi *);
 
 /* ax25_dev.c */
-extern ax25_dev *ax25_dev_list;
 extern spinlock_t ax25_dev_lock;
 
 #if IS_ENABLED(CONFIG_AX25)
diff --git a/net/ax25/ax25_dev.c b/net/ax25/ax25_dev.c
index 282ec581c0720..f16ee5c09d07a 100644
--- a/net/ax25/ax25_dev.c
+++ b/net/ax25/ax25_dev.c
@@ -22,11 +22,12 @@
 #include <net/sock.h>
 #include <linux/uaccess.h>
 #include <linux/fcntl.h>
+#include <linux/list.h>
 #include <linux/mm.h>
 #include <linux/interrupt.h>
 #include <linux/init.h>
 
-ax25_dev *ax25_dev_list;
+static LIST_HEAD(ax25_dev_list);
 DEFINE_SPINLOCK(ax25_dev_lock);
 
 ax25_dev *ax25_addr_ax25dev(ax25_address *addr)
@@ -34,7 +35,7 @@ ax25_dev *ax25_addr_ax25dev(ax25_address *addr)
 	ax25_dev *ax25_dev, *res = NULL;
 
 	spin_lock_bh(&ax25_dev_lock);
-	for (ax25_dev = ax25_dev_list; ax25_dev != NULL; ax25_dev = ax25_dev->next)
+	list_for_each_entry(ax25_dev, &ax25_dev_list, list)
 		if (ax25cmp(addr, (const ax25_address *)ax25_dev->dev->dev_addr) == 0) {
 			res = ax25_dev;
 			ax25_dev_hold(ax25_dev);
@@ -59,7 +60,6 @@ void ax25_dev_device_up(struct net_device *dev)
 	}
 
 	refcount_set(&ax25_dev->refcount, 1);
-	dev->ax25_ptr     = ax25_dev;
 	ax25_dev->dev     = dev;
 	netdev_hold(dev, &ax25_dev->dev_tracker, GFP_KERNEL);
 	ax25_dev->forward = NULL;
@@ -85,8 +85,8 @@ void ax25_dev_device_up(struct net_device *dev)
 #endif
 
 	spin_lock_bh(&ax25_dev_lock);
-	ax25_dev->next = ax25_dev_list;
-	ax25_dev_list  = ax25_dev;
+	list_add(&ax25_dev->list, &ax25_dev_list);
+	dev->ax25_ptr     = ax25_dev;
 	spin_unlock_bh(&ax25_dev_lock);
 	ax25_dev_hold(ax25_dev);
 
@@ -111,32 +111,25 @@ void ax25_dev_device_down(struct net_device *dev)
 	/*
 	 *	Remove any packet forwarding that points to this device.
 	 */
-	for (s = ax25_dev_list; s != NULL; s = s->next)
+	list_for_each_entry(s, &ax25_dev_list, list)
 		if (s->forward == dev)
 			s->forward = NULL;
 
-	if ((s = ax25_dev_list) == ax25_dev) {
-		ax25_dev_list = s->next;
-		goto unlock_put;
-	}
-
-	while (s != NULL && s->next != NULL) {
-		if (s->next == ax25_dev) {
-			s->next = ax25_dev->next;
+	list_for_each_entry(s, &ax25_dev_list, list) {
+		if (s == ax25_dev) {
+			list_del(&s->list);
 			goto unlock_put;
 		}
-
-		s = s->next;
 	}
-	spin_unlock_bh(&ax25_dev_lock);
 	dev->ax25_ptr = NULL;
+	spin_unlock_bh(&ax25_dev_lock);
 	ax25_dev_put(ax25_dev);
 	return;
 
 unlock_put:
+	dev->ax25_ptr = NULL;
 	spin_unlock_bh(&ax25_dev_lock);
 	ax25_dev_put(ax25_dev);
-	dev->ax25_ptr = NULL;
 	netdev_put(dev, &ax25_dev->dev_tracker);
 	ax25_dev_put(ax25_dev);
 }
@@ -200,16 +193,13 @@ struct net_device *ax25_fwd_dev(struct net_device *dev)
  */
 void __exit ax25_dev_free(void)
 {
-	ax25_dev *s, *ax25_dev;
+	ax25_dev *s, *n;
 
 	spin_lock_bh(&ax25_dev_lock);
-	ax25_dev = ax25_dev_list;
-	while (ax25_dev != NULL) {
-		s        = ax25_dev;
-		netdev_put(ax25_dev->dev, &ax25_dev->dev_tracker);
-		ax25_dev = ax25_dev->next;
+	list_for_each_entry_safe(s, n, &ax25_dev_list, list) {
+		netdev_put(s->dev, &s->dev_tracker);
+		list_del(&s->list);
 		kfree(s);
 	}
-	ax25_dev_list = NULL;
 	spin_unlock_bh(&ax25_dev_lock);
 }




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