[PATCH net v3 1/2] ax25: Fix reference count leak issues of ax25_dev and net_device
From: Duoming Zhou <hidden>
Date: 2024-05-06 14:09:16
Also in:
linux-hams, lkml
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
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 <redacted>
Signed-off-by: Duoming Zhou <redacted>
---
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