From: Duoming Zhou duoming@zju.edu.cn
commit 5352a761308397a0e6250fdc629bb3f615b94747 upstream.
There are UAF bugs in ax25_send_control(), when we call ax25_release() to deallocate ax25_dev. The possible race condition is shown below:
(Thread 1) | (Thread 2) ax25_dev_device_up() //(1) | | ax25_kill_by_device() ax25_bind() //(2) | ax25_connect() | ... ax25->state = AX25_STATE_1 | ... | ax25_dev_device_down() //(3)
(Thread 3) ax25_release() | ax25_dev_put() //(4) FREE | case AX25_STATE_1: | ax25_send_control() | alloc_skb() //USE |
The refcount of ax25_dev increases in position (1) and (2), and decreases in position (3) and (4). The ax25_dev will be freed before dereference sites in ax25_send_control().
The following is part of the report:
[ 102.297448] BUG: KASAN: use-after-free in ax25_send_control+0x33/0x210 [ 102.297448] Read of size 8 at addr ffff888009e6e408 by task ax25_close/602 [ 102.297448] Call Trace: [ 102.303751] ax25_send_control+0x33/0x210 [ 102.303751] ax25_release+0x356/0x450 [ 102.305431] __sock_release+0x6d/0x120 [ 102.305431] sock_close+0xf/0x20 [ 102.305431] __fput+0x11f/0x420 [ 102.305431] task_work_run+0x86/0xd0 [ 102.307130] get_signal+0x1075/0x1220 [ 102.308253] arch_do_signal_or_restart+0x1df/0xc00 [ 102.308253] exit_to_user_mode_prepare+0x150/0x1e0 [ 102.308253] syscall_exit_to_user_mode+0x19/0x50 [ 102.308253] do_syscall_64+0x48/0x90 [ 102.308253] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 102.308253] RIP: 0033:0x405ae7
This patch defers the free operation of ax25_dev and net_device after all corresponding dereference sites in ax25_release() to avoid UAF.
Fixes: 9fd75b66b8f6 ("ax25: Fix refcount leaks caused by ax25_cb_del()") Signed-off-by: Duoming Zhou duoming@zju.edu.cn Signed-off-by: Paolo Abeni pabeni@redhat.com [OP: backport to 4.19: adjust dev_put_track()->dev_put()] Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com --- net/ax25/af_ax25.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index 4c41c91227b2..6d08b8ef4219 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -993,10 +993,6 @@ static int ax25_release(struct socket *sock) sock_orphan(sk); ax25 = sk_to_ax25(sk); ax25_dev = ax25->ax25_dev; - if (ax25_dev) { - dev_put(ax25_dev->dev); - ax25_dev_put(ax25_dev); - }
if (sk->sk_type == SOCK_SEQPACKET) { switch (ax25->state) { @@ -1058,6 +1054,10 @@ static int ax25_release(struct socket *sock) sk->sk_state_change(sk); ax25_destroy_socket(ax25); } + if (ax25_dev) { + dev_put(ax25_dev->dev); + ax25_dev_put(ax25_dev); + }
sock->sk = NULL; release_sock(sk);