From c0e93a6d36135d5082cb3af8352f5b69c9f58d6e Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Sat, 29 Dec 2018 13:56:36 -0800 Subject: 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 Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ax25/ax25_dev.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'net/ax25/ax25_dev.c') diff --git a/net/ax25/ax25_dev.c b/net/ax25/ax25_dev.c index 3d106767b272..5faca5db6385 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; -- cgit v1.2.3