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Date: Fri, 28 Jan 2022 12:47:16 +0800
From: Duoming Zhou <duoming@....edu.cn>
To: linux-hams@...r.kernel.org
Cc: jreuter@...na.de, ralf@...ux-mips.org, davem@...emloft.net,
kuba@...nel.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, Duoming Zhou <duoming@....edu.cn>
Subject: [PATCH 2/2] ax25: add refcount in ax25_dev to avoid UAF bugs
If we dereference ax25_dev after we call kfree(ax25_dev) in
ax25_dev_device_down(), it will lead to concurrency UAF bugs.
There are eight syscall functions suffer from UAF bugs, include
ax25_bind(), ax25_release(), ax25_connect(), ax25_ioctl(),
ax25_getname(), ax25_sendmsg(), ax25_getsockopt() and
ax25_info_show().
One of the concurrency UAF can be shown as below:
(USE) | (FREE)
| ax25_device_event
| ax25_dev_device_down
ax25_bind | ...
... | kfree(ax25_dev)
ax25_fillin_cb() | ...
ax25_fillin_cb_from_dev() |
... |
The root cause of UAF bugs is that kfree(ax25_dev) in
ax25_dev_device_down() is not protected by any locks.
When ax25_dev, which there are still pointers point to,
is released, the concurrency UAF bug will happen.
This patch introduces refcount into ax25_dev in order to
guarantee that there are no pointers point to it when ax25_dev
is released.
Signed-off-by: Duoming Zhou <duoming@....edu.cn>
---
include/net/ax25.h | 10 ++++++++++
net/ax25/af_ax25.c | 2 ++
net/ax25/ax25_dev.c | 12 ++++++++++--
net/ax25/ax25_route.c | 3 +++
4 files changed, 25 insertions(+), 2 deletions(-)
diff --git a/include/net/ax25.h b/include/net/ax25.h
index 526e4958919..50b417df622 100644
--- a/include/net/ax25.h
+++ b/include/net/ax25.h
@@ -239,6 +239,7 @@ typedef struct ax25_dev {
#if defined(CONFIG_AX25_DAMA_SLAVE) || defined(CONFIG_AX25_DAMA_MASTER)
ax25_dama_info dama;
#endif
+ refcount_t refcount;
} ax25_dev;
typedef struct ax25_cb {
@@ -293,6 +294,15 @@ static __inline__ void ax25_cb_put(ax25_cb *ax25)
}
}
+#define ax25_dev_hold(__ax25_dev) \
+ refcount_inc(&((__ax25_dev)->refcount))
+
+static __inline__ void ax25_dev_put(ax25_dev *ax25_dev)
+{
+ if (refcount_dec_and_test(&ax25_dev->refcount)) {
+ kfree(ax25_dev);
+ }
+}
static inline __be16 ax25_type_trans(struct sk_buff *skb, struct net_device *dev)
{
skb->dev = dev;
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index 44a8730c26a..32f61978ff2 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -91,6 +91,7 @@ static void ax25_kill_by_device(struct net_device *dev)
spin_unlock_bh(&ax25_list_lock);
lock_sock(sk);
s->ax25_dev = NULL;
+ ax25_dev_put(ax25_dev);
release_sock(sk);
ax25_disconnect(s, ENETUNREACH);
spin_lock_bh(&ax25_list_lock);
@@ -439,6 +440,7 @@ static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg)
}
out_put:
+ ax25_dev_put(ax25_dev);
ax25_cb_put(ax25);
return ret;
diff --git a/net/ax25/ax25_dev.c b/net/ax25/ax25_dev.c
index 256fadb94df..770b787fb7b 100644
--- a/net/ax25/ax25_dev.c
+++ b/net/ax25/ax25_dev.c
@@ -37,6 +37,7 @@ ax25_dev *ax25_addr_ax25dev(ax25_address *addr)
for (ax25_dev = ax25_dev_list; ax25_dev != NULL; ax25_dev = ax25_dev->next)
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);
@@ -56,6 +57,7 @@ void ax25_dev_device_up(struct net_device *dev)
return;
}
+ refcount_set(&ax25_dev->refcount, 1);
dev->ax25_ptr = ax25_dev;
ax25_dev->dev = dev;
dev_hold_track(dev, &ax25_dev->dev_tracker, GFP_ATOMIC);
@@ -83,6 +85,7 @@ void ax25_dev_device_up(struct net_device *dev)
spin_lock_bh(&ax25_dev_lock);
ax25_dev->next = ax25_dev_list;
ax25_dev_list = ax25_dev;
+ ax25_dev_hold(ax25_dev);
spin_unlock_bh(&ax25_dev_lock);
ax25_register_dev_sysctl(ax25_dev);
@@ -112,20 +115,22 @@ void ax25_dev_device_down(struct net_device *dev)
if ((s = ax25_dev_list) == ax25_dev) {
ax25_dev_list = s->next;
+ ax25_dev_put(ax25_dev);
spin_unlock_bh(&ax25_dev_lock);
dev->ax25_ptr = NULL;
dev_put_track(dev, &ax25_dev->dev_tracker);
- kfree(ax25_dev);
+ ax25_dev_put(ax25_dev);
return;
}
while (s != NULL && s->next != NULL) {
if (s->next == ax25_dev) {
s->next = ax25_dev->next;
+ ax25_dev_put(ax25_dev);
spin_unlock_bh(&ax25_dev_lock);
dev->ax25_ptr = NULL;
dev_put_track(dev, &ax25_dev->dev_tracker);
- kfree(ax25_dev);
+ ax25_dev_put(ax25_dev);
return;
}
@@ -133,6 +138,7 @@ void ax25_dev_device_down(struct net_device *dev)
}
spin_unlock_bh(&ax25_dev_lock);
dev->ax25_ptr = NULL;
+ ax25_dev_put(ax25_dev);
}
int ax25_fwd_ioctl(unsigned int cmd, struct ax25_fwd_struct *fwd)
@@ -149,6 +155,7 @@ int ax25_fwd_ioctl(unsigned int cmd, struct ax25_fwd_struct *fwd)
if (ax25_dev->forward != NULL)
return -EINVAL;
ax25_dev->forward = fwd_dev->dev;
+ ax25_dev_put(fwd_dev);
break;
case SIOCAX25DELFWD:
@@ -161,6 +168,7 @@ int ax25_fwd_ioctl(unsigned int cmd, struct ax25_fwd_struct *fwd)
return -EINVAL;
}
+ ax25_dev_put(ax25_dev);
return 0;
}
diff --git a/net/ax25/ax25_route.c b/net/ax25/ax25_route.c
index d0b2e094bd5..1e32693833e 100644
--- a/net/ax25/ax25_route.c
+++ b/net/ax25/ax25_route.c
@@ -116,6 +116,7 @@ static int __must_check ax25_rt_add(struct ax25_routes_struct *route)
ax25_rt->dev = ax25_dev->dev;
ax25_rt->digipeat = NULL;
ax25_rt->ip_mode = ' ';
+ ax25_dev_put(ax25_dev);
if (route->digi_count != 0) {
if ((ax25_rt->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
write_unlock_bh(&ax25_route_lock);
@@ -172,6 +173,7 @@ static int ax25_rt_del(struct ax25_routes_struct *route)
}
}
}
+ ax25_dev_put(ax25_dev);
write_unlock_bh(&ax25_route_lock);
return 0;
@@ -214,6 +216,7 @@ static int ax25_rt_opt(struct ax25_route_opt_struct *rt_option)
}
out:
+ ax25_dev_put(ax25_dev);
write_unlock_bh(&ax25_route_lock);
return err;
}
--
2.17.1
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