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Date: Thu, 2 May 2024 10:56:43 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: duoming@....edu.cn
Cc: linux-hams@...r.kernel.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, pabeni@...hat.com, kuba@...nel.org,
edumazet@...gle.com, davem@...emloft.net, jreuter@...na.de,
lars@...bit.com, Miroslav Skoric <skoric@....ac.rs>
Subject: Re: [PATCH net] ax25: Fix refcount leak issues of ax25_dev
On Thu, May 02, 2024 at 12:35:44PM +0800, duoming@....edu.cn wrote:
> On Wed, 1 May 2024 20:43:37 +0300 Dan Carpenter wrote:
> > I'm always happy to take credit for stuff but the Reported by should go
> > to Lars and Miroslav.
> >
> > Reported-by: Lars Kellogg-Stedman <lars@...bit.com>
> > Reported-by: Miroslav Skoric <skoric@....ac.rs>
>
> This patch is not related with the problem raised by Lars Kellogg-Stedman
> and Miroslav Skoric, it only solves the reference counting leak issues of
> ax25_dev in ax25_addr_ax25dev() and ax25_dev_device_down(). So I think
> there is no need to change the "Reported by" label.
>
Ah... I was really hoping it was related to the other bugs.
Okay, what about we separate this into different patches one for each
bug? The changes to ax25_addr_ax25dev() and ax25_dev_free() are
obvious and could go in as-is but as two separate patches.
The changes to ax25_dev_device_up/down() are more subtle.
The ax25_dev_list stuff is frustrating. It would be so much easier if
it were a normal list and you could just do:
/*
* Remove any packet forwarding that points to this device.
*/
list_for_each_entry(s, ax25_dev_list, list) {
if (s->forward == dev)
s->forward = NULL;
}
list_for_each_entry(s, ax25_dev_list, list) {
if (s == ax25_dev) {
list_del(s);
free_net = true;
break;
}
}
spin_unlock_bh(&ax25_dev_lock);
dev->ax25_ptr = NULL;
if (free_net)
netdev_put(dev, &ax25_dev->dev_tracker);
ax25_dev_put(ax25_dev);
}
Why do we call netdev_put() on that one path? Btw, here is an untested
conversion to lists...
regards,
dan carpenter
diff --git a/include/net/ax25.h b/include/net/ax25.h
index 0d939e5aee4e..c2a85fd3f5ea 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 282ec581c072..b632af38f1e1 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 struct list_head ax25_dev_list;
DEFINE_SPINLOCK(ax25_dev_lock);
ax25_dev *ax25_addr_ax25dev(ax25_address *addr)
@@ -34,11 +35,12 @@ 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);
}
+ }
spin_unlock_bh(&ax25_dev_lock);
return res;
@@ -52,6 +54,10 @@ void ax25_dev_device_up(struct net_device *dev)
{
ax25_dev *ax25_dev;
+ // FIXME: do call this in probe or something
+ if (!ax25_dev_list.next)
+ INIT_LIST_HEAD(&ax25_dev_list);
+
ax25_dev = kzalloc(sizeof(*ax25_dev), GFP_KERNEL);
if (!ax25_dev) {
printk(KERN_ERR "AX.25: ax25_dev_device_up - out of memory\n");
@@ -85,8 +91,7 @@ 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);
spin_unlock_bh(&ax25_dev_lock);
ax25_dev_hold(ax25_dev);
@@ -111,23 +116,18 @@ 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;
ax25_dev_put(ax25_dev);
@@ -200,16 +200,13 @@ 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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