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authorDuoming Zhou <duoming@zju.edu.cn>2022-05-30 23:21:58 +0800
committerPaolo Abeni <pabeni@redhat.com>2022-06-02 10:37:57 +0200
commit7d8a3a477b3e25ada8dc71d22048c2ea417209a0 (patch)
tree025a2a93fe99c26fa80090c2aed7a3e66114def0 /net/ax25/af_ax25.c
parent9f4fc18bf285f20c1498f8fcfb586fa70a070fb5 (diff)
ax25: Fix ax25 session cleanup problems
There are session cleanup problems in ax25_release() and ax25_disconnect(). If we setup a session and then disconnect, the disconnected session is still in "LISTENING" state that is shown below. Active AX.25 sockets Dest Source Device State Vr/Vs Send-Q Recv-Q DL9SAU-4 DL9SAU-3 ??? LISTENING 000/000 0 0 DL9SAU-3 DL9SAU-4 ??? LISTENING 000/000 0 0 The first reason is caused by del_timer_sync() in ax25_release(). The timers of ax25 are used for correct session cleanup. If we use ax25_release() to close ax25 sessions and ax25_dev is not null, the del_timer_sync() functions in ax25_release() will execute. As a result, the sessions could not be cleaned up correctly, because the timers have stopped. In order to solve this problem, this patch adds a device_up flag in ax25_dev in order to judge whether the device is up. If there are sessions to be cleaned up, the del_timer_sync() in ax25_release() will not execute. What's more, we add ax25_cb_del() in ax25_kill_by_device(), because the timers have been stopped and there are no functions that could delete ax25_cb if we do not call ax25_release(). Finally, we reorder the position of ax25_list_lock in ax25_cb_del() in order to synchronize among different functions that call ax25_cb_del(). The second reason is caused by improper check in ax25_disconnect(). The incoming ax25 sessions which ax25->sk is null will close heartbeat timer, because the check "if(!ax25->sk || ..)" is satisfied. As a result, the session could not be cleaned up properly. In order to solve this problem, this patch changes the improper check to "if(ax25->sk && ..)" in ax25_disconnect(). What`s more, the ax25_disconnect() may be called twice, which is not necessary. For example, ax25_kill_by_device() calls ax25_disconnect() and sets ax25->state to AX25_STATE_0, but ax25_release() calls ax25_disconnect() again. In order to solve this problem, this patch add a check in ax25_release(). If the flag of ax25->sk equals to SOCK_DEAD, the ax25_disconnect() in ax25_release() should not be executed. Fixes: 82e31755e55f ("ax25: Fix UAF bugs in ax25 timers") Fixes: 8a367e74c012 ("ax25: Fix segfault after sock connection timeout") Reported-and-tested-by: Thomas Osterried <thomas@osterried.de> Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> Link: https://lore.kernel.org/r/20220530152158.108619-1-duoming@zju.edu.cn Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Diffstat (limited to 'net/ax25/af_ax25.c')
-rw-r--r--net/ax25/af_ax25.c27
1 files changed, 17 insertions, 10 deletions
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index 116481e4da82..95393bb2760b 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -62,12 +62,12 @@ static void ax25_free_sock(struct sock *sk)
*/
static void ax25_cb_del(ax25_cb *ax25)
{
+ spin_lock_bh(&ax25_list_lock);
if (!hlist_unhashed(&ax25->ax25_node)) {
- spin_lock_bh(&ax25_list_lock);
hlist_del_init(&ax25->ax25_node);
- spin_unlock_bh(&ax25_list_lock);
ax25_cb_put(ax25);
}
+ spin_unlock_bh(&ax25_list_lock);
}
/*
@@ -81,6 +81,7 @@ static void ax25_kill_by_device(struct net_device *dev)
if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
return;
+ ax25_dev->device_up = false;
spin_lock_bh(&ax25_list_lock);
again:
@@ -91,6 +92,7 @@ again:
spin_unlock_bh(&ax25_list_lock);
ax25_disconnect(s, ENETUNREACH);
s->ax25_dev = NULL;
+ ax25_cb_del(s);
spin_lock_bh(&ax25_list_lock);
goto again;
}
@@ -103,6 +105,7 @@ again:
dev_put_track(ax25_dev->dev, &ax25_dev->dev_tracker);
ax25_dev_put(ax25_dev);
}
+ ax25_cb_del(s);
release_sock(sk);
spin_lock_bh(&ax25_list_lock);
sock_put(sk);
@@ -995,9 +998,11 @@ static int ax25_release(struct socket *sock)
if (sk->sk_type == SOCK_SEQPACKET) {
switch (ax25->state) {
case AX25_STATE_0:
- release_sock(sk);
- ax25_disconnect(ax25, 0);
- lock_sock(sk);
+ if (!sock_flag(ax25->sk, SOCK_DEAD)) {
+ release_sock(sk);
+ ax25_disconnect(ax25, 0);
+ lock_sock(sk);
+ }
ax25_destroy_socket(ax25);
break;
@@ -1053,11 +1058,13 @@ static int ax25_release(struct socket *sock)
ax25_destroy_socket(ax25);
}
if (ax25_dev) {
- del_timer_sync(&ax25->timer);
- del_timer_sync(&ax25->t1timer);
- del_timer_sync(&ax25->t2timer);
- del_timer_sync(&ax25->t3timer);
- del_timer_sync(&ax25->idletimer);
+ if (!ax25_dev->device_up) {
+ del_timer_sync(&ax25->timer);
+ del_timer_sync(&ax25->t1timer);
+ del_timer_sync(&ax25->t2timer);
+ del_timer_sync(&ax25->t3timer);
+ del_timer_sync(&ax25->idletimer);
+ }
dev_put_track(ax25_dev->dev, &ax25_dev->dev_tracker);
ax25_dev_put(ax25_dev);
}