From: Duoming Zhou <duoming@zju.edu.cn> stable inclusion from linux-5.10.106 commit e2201ef32f933944ee02e59205adb566bafcdf91 category: bugfix bugzilla: 186561 https://gitee.com/src-openeuler/kernel/issues/I53VJO CVE: CVE-2022-1199 -------------------------------- [ 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> Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com> Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com> Reviewed-by: Wei Yongjun <weiyongjun1@huawei.com> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- 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 cbedc33f8b27..e5f6838a235a 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); -- 2.20.1