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Date: Mon, 6 May 2024 22:08:34 +0800
From: Duoming Zhou <duoming@....edu.cn>
To: netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
linux-hams@...r.kernel.org,
pabeni@...hat.com,
kuba@...nel.org,
edumazet@...gle.com,
davem@...emloft.net,
jreuter@...na.de,
horms@...nel.org,
Markus.Elfring@....de,
dan.carpenter@...aro.org,
lars@...bit.com,
Duoming Zhou <duoming@....edu.cn>
Subject: [PATCH net v3 1/2] ax25: Fix reference count leak issues of ax25_dev and net_device
The ax25_addr_ax25dev() exists a reference count leak issue of the
object "ax25_dev" and the ax25_dev_device_down() exists reference
count leak issues of the objects "ax25_dev" and "net_device".
Memory leak issue in ax25_addr_ax25dev():
The reference count of the object "ax25_dev" can be increased multiple
times in ax25_addr_ax25dev(). This will cause a memory leak so far.
Memory leak issues in ax25_dev_device_down():
The reference count of ax25_dev is set to 1 in ax25_dev_device_up() and
then increase the reference count when ax25_dev is added to ax25_dev_list.
As a result, the reference count of ax25_dev is 2. But when the device is
shutting down. The ax25_dev_device_down() drops the reference count once
or twice depending on if we goto unlock_put or not, which will cause
memory leak.
There is also a reference count leak issue of the object "net_device",
when the ax25 device is shutting down. The ax25_dev_device_down() drops
the reference count of net_device one or zero times depending on if we
goto unlock_put or not, which will cause memory leak.
In order to solve the above issues, use kernel circular doubly linked
list to implementate ax25_dev_list. As for ax25_addr_ax25dev() issue,
it is impossible for one pointer to be on a list twice. So add a break
in ax25_addr_ax25dev(). As for ax25_dev_device_down() issues, increase
the reference count of ax25_dev once in ax25_dev_device_up() and decrease
the reference count of ax25_dev and net_device after ax25_dev is removed
from the ax25_dev_list.
Fixes: d01ffb9eee4a ("ax25: add refcount in ax25_dev to avoid UAF bugs")
Suggested-by: Dan Carpenter <dan.carpenter@...aro.org>
Signed-off-by: Duoming Zhou <duoming@....edu.cn>
---
Changes in v3:
- Use kernel list to implementate ax25_dev_list.
- Solve reference count leak issues in ax25_dev_device_down().
include/net/ax25.h | 4 ++--
net/ax25/ax25_dev.c | 36 ++++++++++++------------------------
2 files changed, 14 insertions(+), 26 deletions(-)
diff --git a/include/net/ax25.h b/include/net/ax25.h
index 0d939e5aee4..92c6aa4f9a6 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 +330,7 @@ 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;
+static struct list_head 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 282ec581c07..fbaaba0351e 100644
--- a/net/ax25/ax25_dev.c
+++ b/net/ax25/ax25_dev.c
@@ -22,11 +22,11 @@
#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;
DEFINE_SPINLOCK(ax25_dev_lock);
ax25_dev *ax25_addr_ax25dev(ax25_address *addr)
@@ -34,11 +34,13 @@ 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);
+ break;
}
+ }
spin_unlock_bh(&ax25_dev_lock);
return res;
@@ -52,6 +54,7 @@ void ax25_dev_device_up(struct net_device *dev)
{
ax25_dev *ax25_dev;
+ 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");
@@ -59,7 +62,6 @@ 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;
@@ -85,10 +87,9 @@ 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);
+ dev->ax25_ptr = ax25_dev;
ax25_register_dev_sysctl(ax25_dev);
}
@@ -111,32 +112,19 @@ 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;
- goto unlock_put;
+ list_for_each_entry(s, &ax25_dev_list, list) {
+ if (s == ax25_dev) {
+ list_del(&s->list);
+ break;
}
-
- s = s->next;
}
- spin_unlock_bh(&ax25_dev_lock);
dev->ax25_ptr = NULL;
- ax25_dev_put(ax25_dev);
- return;
-
-unlock_put:
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);
}
--
2.17.1
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