ax25: fix a use-after-free in ax25_fillin_cb()
[ Upstream commit c433570458e49bccea5c551df628d058b3526289 ]
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/net/ax25/ax25_dev.c b/net/ax25/ax25_dev.c
index 3d10676..5faca5d 100644
--- a/net/ax25/ax25_dev.c
+++ b/net/ax25/ax25_dev.c
@@ -116,6 +116,7 @@
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 @@
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;