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authorCong Wang <xiyou.wangcong@gmail.com>2018-12-29 13:56:36 -0800
committerDavid S. Miller <davem@davemloft.net>2018-12-30 14:07:54 -0800
commitc433570458e49bccea5c551df628d058b3526289 (patch)
tree05427f71af7a74fb15b0eb08f138cc6004a225c1
parent7f334a7e1ae113212e39aafba51352ea9ab8c9f9 (diff)
ax25: fix a use-after-free in ax25_fillin_cb()
There are multiple issues here: 1. After freeing dev->ax25_ptr, we need to set it to NULL otherwise we may use a dangling pointer. 2. There is a race between ax25_setsockopt() and device notifier as reported by syzbot. Close it by holding RTNL lock. 3. We need to test if dev->ax25_ptr is NULL before using it. Reported-and-tested-by: syzbot+ae6bb869cbed29b29040@syzkaller.appspotmail.com Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ax25/af_ax25.c11
-rw-r--r--net/ax25/ax25_dev.c2
2 files changed, 11 insertions, 2 deletions
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index c603d33d5410..5d01edf8d819 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -653,15 +653,22 @@ static int ax25_setsockopt(struct socket *sock, int level, int optname,
break;
}
- dev = dev_get_by_name(&init_net, devname);
+ rtnl_lock();
+ dev = __dev_get_by_name(&init_net, devname);
if (!dev) {
+ rtnl_unlock();
res = -ENODEV;
break;
}
ax25->ax25_dev = ax25_dev_ax25dev(dev);
+ if (!ax25->ax25_dev) {
+ rtnl_unlock();
+ res = -ENODEV;
+ break;
+ }
ax25_fillin_cb(ax25, ax25->ax25_dev);
- dev_put(dev);
+ rtnl_unlock();
break;
default:
diff --git a/net/ax25/ax25_dev.c b/net/ax25/ax25_dev.c
index 9a3a301e1e2f..d92195cd7834 100644
--- a/net/ax25/ax25_dev.c
+++ b/net/ax25/ax25_dev.c
@@ -116,6 +116,7 @@ void ax25_dev_device_down(struct net_device *dev)
if ((s = ax25_dev_list) == ax25_dev) {
ax25_dev_list = s->next;
spin_unlock_bh(&ax25_dev_lock);
+ dev->ax25_ptr = NULL;
dev_put(dev);
kfree(ax25_dev);
return;
@@ -125,6 +126,7 @@ void ax25_dev_device_down(struct net_device *dev)
if (s->next == ax25_dev) {
s->next = ax25_dev->next;
spin_unlock_bh(&ax25_dev_lock);
+ dev->ax25_ptr = NULL;
dev_put(dev);
kfree(ax25_dev);
return;

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