From: Duoming Zhou duoming@zju.edu.cn
[ Upstream commit 71171ac8eb34ce7fe6b3267dce27c313ab3cb3ac ]
When two ax25 devices attempted to establish connection, the requester use ax25_create(), ax25_bind() and ax25_connect() to initiate connection. The receiver use ax25_rcv() to accept connection and use ax25_create_cb() in ax25_rcv() to create ax25_cb, but the ax25_cb->sk is NULL. When the receiver is detaching, a NULL pointer dereference bug caused by sock_hold(sk) in ax25_kill_by_device() will happen. The corresponding fail log is shown below:
=============================================================== BUG: KASAN: null-ptr-deref in ax25_device_event+0xfd/0x290 Call Trace: ... ax25_device_event+0xfd/0x290 raw_notifier_call_chain+0x5e/0x70 dev_close_many+0x174/0x220 unregister_netdevice_many+0x1f7/0xa60 unregister_netdevice_queue+0x12f/0x170 unregister_netdev+0x13/0x20 mkiss_close+0xcd/0x140 tty_ldisc_release+0xc0/0x220 tty_release_struct+0x17/0xa0 tty_release+0x62d/0x670 ...
This patch add condition check in ax25_kill_by_device(). If s->sk is NULL, it will goto if branch to kill device.
Fixes: 4e0f718daf97 ("ax25: improve the incomplete fix to avoid UAF and NPD bugs") Reported-by: Thomas Osterried thomas@osterried.de Signed-off-by: Duoming Zhou duoming@zju.edu.cn Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/ax25/af_ax25.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index 44a8730c26ac..00bb087c2ca8 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -87,6 +87,13 @@ static void ax25_kill_by_device(struct net_device *dev) ax25_for_each(s, &ax25_list) { if (s->ax25_dev == ax25_dev) { sk = s->sk; + if (!sk) { + spin_unlock_bh(&ax25_list_lock); + s->ax25_dev = NULL; + ax25_disconnect(s, ENETUNREACH); + spin_lock_bh(&ax25_list_lock); + goto again; + } sock_hold(sk); spin_unlock_bh(&ax25_list_lock); lock_sock(sk);