Thread (2 messages) 2 messages, 2 authors, 2022-02-02

Re: [Fixes] ax25: add refcount in ax25_dev to avoid UAF bugs

From: Dan Carpenter <hidden>
Date: 2022-02-02 17:47:44
Also in: linux-hams, lkml 

Hi Duoming Zhou,

The original patch was already applied so you need to just send the
fixes by themselves on top of the net-next git tree.
quoted hunk ↗ jump to hunk
---
 include/net/ax25.h    | 12 ++++++++++++
 net/ax25/af_ax25.c    | 20 ++++++++++++++++----
 net/ax25/ax25_dev.c   | 33 +++++++++++++++++++++++++++------
 net/ax25/ax25_route.c | 27 ++++++++++++++++++++++-----
 4 files changed, 77 insertions(+), 15 deletions(-)

diff --git a/include/net/ax25.h b/include/net/ax25.h
index 526e4958919..1a38b1ad529 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 +294,17 @@ static __inline__ void ax25_cb_put(ax25_cb *ax25)
 	}
 }
 
+static inline void ax25_dev_hold(ax25_dev *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);
+}
+
Forget about these cleanups for now.  Just fix the reference leaks on
error.
quoted hunk ↗ jump to hunk
 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..7463bbd4e63 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);
@@ -358,21 +359,31 @@ static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg)
 	if (copy_from_user(&ax25_ctl, arg, sizeof(ax25_ctl)))
 		return -EFAULT;
 
-	if ((ax25_dev = ax25_addr_ax25dev(&ax25_ctl.port_addr)) == NULL)
+	ax25_dev = ax25_addr_ax25dev(&ax25_ctl.port_addr);
+	if (ax25_dev == NULL) {
+		ax25_dev_put(ax25_dev);
This one will lead to a NULL dereference.  These NULL dereferences are

 		return -ENODEV;
+	}
 
-	if (ax25_ctl.digi_count > AX25_MAX_DIGIS)
+	if (ax25_ctl.digi_count > AX25_MAX_DIGIS) {
+		ax25_dev_put(ax25_dev);
 		return -EINVAL;
+	}
 
-	if (ax25_ctl.arg > ULONG_MAX / HZ && ax25_ctl.cmd != AX25_KILL)
+	if (ax25_ctl.arg > ULONG_MAX / HZ && ax25_ctl.cmd != AX25_KILL) {
+		ax25_dev_put(ax25_dev);
 		return -EINVAL;
+	}
 
 	digi.ndigi = ax25_ctl.digi_count;
 	for (k = 0; k < digi.ndigi; k++)
 		digi.calls[k] = ax25_ctl.digi_addr[k];
 
-	if ((ax25 = ax25_find_cb(&ax25_ctl.source_addr, &ax25_ctl.dest_addr, &digi, ax25_dev->dev)) == NULL)
+	ax25 = ax25_find_cb(&ax25_ctl.source_addr, &ax25_ctl.dest_addr, &digi, ax25_dev->dev);
+	if (ax25 == NULL) {
+		ax25_dev_put(ax25_dev);
Don't do this.
quoted hunk ↗ jump to hunk
 		return -ENOTCONN;
+	}
 
 	switch (ax25_ctl.cmd) {
 	case AX25_KILL:
@@ -439,6 +450,7 @@ 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..77d9aa2ccab 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);
@@ -111,21 +114,23 @@ void ax25_dev_device_down(struct net_device *dev)
 			s->forward = NULL;
 
 	if ((s = ax25_dev_list) == ax25_dev) {
+		ax25_dev_put(ax25_dev_list);
Just leave the style changes until later.  I'm sorry I brought it up.
quoted hunk ↗ jump to hunk
 		ax25_dev_list = s->next;
 		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) {
+			ax25_dev_put(s->next);
 			s->next = ax25_dev->next;
 			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;
 		}
 
@@ -133,31 +138,47 @@ 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)
 {
 	ax25_dev *ax25_dev, *fwd_dev;
 
-	if ((ax25_dev = ax25_addr_ax25dev(&fwd->port_from)) == NULL)
+	ax25_dev = ax25_addr_ax25dev(&fwd->port_from);
+	if (ax25_dev == NULL) {
+		ax25_dev_put(ax25_dev);
NULL dereference.

 		return -EINVAL;
+	}
 
 	switch (cmd) {
 	case SIOCAX25ADDFWD:
-		if ((fwd_dev = ax25_addr_ax25dev(&fwd->port_to)) == NULL)
+		fwd_dev = ax25_addr_ax25dev(&fwd->port_to);
+		if (fwd_dev == NULL) {
+			ax25_dev_put(fwd_dev);
NULL dereference.

+			ax25_dev_put(ax25_dev);
 			return -EINVAL;
-		if (ax25_dev->forward != NULL)
+		}
+		if (ax25_dev->forward != NULL) {
+			ax25_dev_put(ax25_dev);
Drop the fwd_dev reference as well.
quoted hunk ↗ jump to hunk
 			return -EINVAL;
+		}
 		ax25_dev->forward = fwd_dev->dev;
+		ax25_dev_put(fwd_dev);
+		ax25_dev_put(ax25_dev);
 		break;
 
 	case SIOCAX25DELFWD:
-		if (ax25_dev->forward == NULL)
+		if (ax25_dev->forward == NULL) {
+			ax25_dev_put(ax25_dev);
 			return -EINVAL;
+		}
 		ax25_dev->forward = NULL;
+		ax25_dev_put(ax25_dev);
 		break;
 
 	default:
+		ax25_dev_put(ax25_dev);
 		return -EINVAL;
 	}
 
diff --git a/net/ax25/ax25_route.c b/net/ax25/ax25_route.c
index d0b2e094bd5..7fe7a83b2a3 100644
--- a/net/ax25/ax25_route.c
+++ b/net/ax25/ax25_route.c
@@ -75,10 +75,15 @@ static int __must_check ax25_rt_add(struct ax25_routes_struct *route)
 	ax25_dev *ax25_dev;
 	int i;
 
-	if ((ax25_dev = ax25_addr_ax25dev(&route->port_addr)) == NULL)
+	ax25_dev = ax25_addr_ax25dev(&route->port_addr);
+	if (ax25_dev == NULL) {
+		ax25_dev_put(ax25_dev);
NULL dereference.
quoted hunk ↗ jump to hunk
 		return -EINVAL;
-	if (route->digi_count > AX25_MAX_DIGIS)
+	}
+	if (route->digi_count > AX25_MAX_DIGIS) {
+		ax25_dev_put(ax25_dev);
 		return -EINVAL;
+	}
 
 	write_lock_bh(&ax25_route_lock);
 
@@ -91,6 +96,7 @@ static int __must_check ax25_rt_add(struct ax25_routes_struct *route)
 			if (route->digi_count != 0) {
 				if ((ax25_rt->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
 					write_unlock_bh(&ax25_route_lock);
+					ax25_dev_put(ax25_dev);
 					return -ENOMEM;
 				}
 				ax25_rt->digipeat->lastrepeat = -1;
@@ -101,6 +107,7 @@ static int __must_check ax25_rt_add(struct ax25_routes_struct *route)
 				}
 			}
 			write_unlock_bh(&ax25_route_lock);
+			ax25_dev_put(ax25_dev);
 			return 0;
 		}
 		ax25_rt = ax25_rt->next;
@@ -108,6 +115,7 @@ static int __must_check ax25_rt_add(struct ax25_routes_struct *route)
 
 	if ((ax25_rt = kmalloc(sizeof(ax25_route), GFP_ATOMIC)) == NULL) {
 		write_unlock_bh(&ax25_route_lock);
+		ax25_dev_put(ax25_dev);
 		return -ENOMEM;
 	}
 
@@ -120,6 +128,7 @@ static int __must_check ax25_rt_add(struct ax25_routes_struct *route)
 		if ((ax25_rt->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
 			write_unlock_bh(&ax25_route_lock);
 			kfree(ax25_rt);
+			ax25_dev_put(ax25_dev);
 			return -ENOMEM;
 		}
 		ax25_rt->digipeat->lastrepeat = -1;
@@ -132,6 +141,7 @@ static int __must_check ax25_rt_add(struct ax25_routes_struct *route)
 	ax25_rt->next   = ax25_route_list;
 	ax25_route_list = ax25_rt;
 	write_unlock_bh(&ax25_route_lock);
+	ax25_dev_put(ax25_dev);
 
 	return 0;
 }
@@ -147,8 +157,11 @@ static int ax25_rt_del(struct ax25_routes_struct *route)
 	ax25_route *s, *t, *ax25_rt;
 	ax25_dev *ax25_dev;
 
-	if ((ax25_dev = ax25_addr_ax25dev(&route->port_addr)) == NULL)
+	ax25_dev = ax25_addr_ax25dev(&route->port_addr);
+	if (ax25_dev == NULL) {
+		ax25_dev_put(ax25_dev);
NULL dereference.
quoted hunk ↗ jump to hunk
 		return -EINVAL;
+	}
 
 	write_lock_bh(&ax25_route_lock);
 
@@ -173,7 +186,7 @@ static int ax25_rt_del(struct ax25_routes_struct *route)
 		}
 	}
 	write_unlock_bh(&ax25_route_lock);
-
+	ax25_dev_put(ax25_dev);
 	return 0;
 }
 
@@ -183,8 +196,11 @@ static int ax25_rt_opt(struct ax25_route_opt_struct *rt_option)
 	ax25_dev *ax25_dev;
 	int err = 0;
 
-	if ((ax25_dev = ax25_addr_ax25dev(&rt_option->port_addr)) == NULL)
+	ax25_dev = ax25_addr_ax25dev(&rt_option->port_addr);
+	if (ax25_dev == NULL) {
+		ax25_dev_put(ax25_dev);
NULL dereference.
quoted hunk ↗ jump to hunk
 		return -EINVAL;
+	}
 
 	write_lock_bh(&ax25_route_lock);
 
@@ -215,6 +231,7 @@ static int ax25_rt_opt(struct ax25_route_opt_struct *rt_option)
 
 out:
 	write_unlock_bh(&ax25_route_lock);
+	ax25_dev_put(ax25_dev);
 	return err;
 }
Thanks for this, but please can you resend with the above issues fixed
and based on top of net-next.

regards,
dan carpenter
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