Messages in this thread Patch in this message | | | From | Duoming Zhou <> | Subject | [PATCH net v3] ax25: Fix ax25 session cleanup problem in ax25_release | Date | Sat, 28 May 2022 22:55:20 +0800 |
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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.
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().
Fixes: 82e31755e55f ("ax25: Fix UAF bugs in ax25 timers") Reported-and-tested-by: Thomas Osterried <thomas@osterried.de> Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> --- Changes in v3: - Mitigate race conditions through lock.
include/net/ax25.h | 1 + net/ax25/af_ax25.c | 19 ++++++++++++------- net/ax25/ax25_dev.c | 1 + 3 files changed, 14 insertions(+), 7 deletions(-)
diff --git a/include/net/ax25.h b/include/net/ax25.h index 0f9790c455b..a427a05672e 100644 --- a/include/net/ax25.h +++ b/include/net/ax25.h @@ -228,6 +228,7 @@ 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 363d47f9453..a5b2cd6ce37 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); @@ -1053,11 +1056,13 @@ 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 d2a244e1c26..5451be15e07 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; -- 2.17.1
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