From 7d8a3a477b3e25ada8dc71d22048c2ea417209a0 Mon Sep 17 00:00:00 2001 From: Duoming Zhou Date: Mon, 30 May 2022 23:21:58 +0800 Subject: 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 Signed-off-by: Duoming Zhou Link: https://lore.kernel.org/r/20220530152158.108619-1-duoming@zju.edu.cn Signed-off-by: Paolo Abeni --- net/ax25/af_ax25.c | 27 +++++++++++++++++---------- 1 file changed, 17 insertions(+), 10 deletions(-) (limited to 'net/ax25/af_ax25.c') 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); } -- cgit