lkml.org 
[lkml]   [2019]   [Jan]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.4 16/88] ax25: fix a use-after-free in ax25_fillin_cb()
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Cong Wang <xiyou.wangcong@gmail.com>

[ 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>
---
net/ax25/af_ax25.c | 11 +++++++++--
net/ax25/ax25_dev.c | 2 ++
2 files changed, 11 insertions(+), 2 deletions(-)

--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -654,15 +654,22 @@ static int ax25_setsockopt(struct socket
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:
--- a/net/ax25/ax25_dev.c
+++ b/net/ax25/ax25_dev.c
@@ -116,6 +116,7 @@ void ax25_dev_device_down(struct net_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_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;

\
 
 \ /
  Last update: 2019-01-11 16:11    [W:0.278 / U:0.964 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site