From: Duoming Zhou duoming@zju.edu.cn
[ Upstream commit 7d8a3a477b3e25ada8dc71d22048c2ea417209a0 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/ax25.h | 1 + net/ax25/af_ax25.c | 27 +++++++++++++++++---------- net/ax25/ax25_dev.c | 1 + net/ax25/ax25_subr.c | 2 +- 4 files changed, 20 insertions(+), 11 deletions(-)
diff --git a/include/net/ax25.h b/include/net/ax25.h index 8221af1811df..5253692db9eb 100644 --- a/include/net/ax25.h +++ b/include/net/ax25.h @@ -240,6 +240,7 @@ typedef struct ax25_dev { ax25_dama_info dama; #endif refcount_t refcount; + bool device_up; } ax25_dev;
typedef struct ax25_cb { diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index 363d47f94532..289f355e1853 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 @@ static void ax25_kill_by_device(struct net_device *dev) 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 @@ static void ax25_kill_by_device(struct net_device *dev) 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); } diff --git a/net/ax25/ax25_dev.c b/net/ax25/ax25_dev.c index d2a244e1c260..5451be15e072 100644 --- a/net/ax25/ax25_dev.c +++ b/net/ax25/ax25_dev.c @@ -62,6 +62,7 @@ void ax25_dev_device_up(struct net_device *dev) ax25_dev->dev = dev; dev_hold_track(dev, &ax25_dev->dev_tracker, GFP_ATOMIC); ax25_dev->forward = NULL; + ax25_dev->device_up = true;
ax25_dev->values[AX25_VALUES_IPDEFMODE] = AX25_DEF_IPDEFMODE; ax25_dev->values[AX25_VALUES_AXDEFMODE] = AX25_DEF_AXDEFMODE; diff --git a/net/ax25/ax25_subr.c b/net/ax25/ax25_subr.c index 3a476e4f6cd0..9ff98f46dc6b 100644 --- a/net/ax25/ax25_subr.c +++ b/net/ax25/ax25_subr.c @@ -268,7 +268,7 @@ void ax25_disconnect(ax25_cb *ax25, int reason) del_timer_sync(&ax25->t3timer); del_timer_sync(&ax25->idletimer); } else { - if (!ax25->sk || !sock_flag(ax25->sk, SOCK_DESTROY)) + if (ax25->sk && !sock_flag(ax25->sk, SOCK_DESTROY)) ax25_stop_heartbeat(ax25); ax25_stop_t1timer(ax25); ax25_stop_t2timer(ax25);