From d6ab327da8d4917c9519198cff80064843d418e2 Mon Sep 17 00:00:00 2001 From: Lin Ma Date: Wed, 26 Jan 2022 16:44:37 +0800 Subject: [PATCH] ax25: NPD bug when detaching AX25 device stable inclusion from stable-v5.10.89 commit 8e34d07dd4d9f7811d8ae35adee24e78a4576844 bugzilla: 186140 https://gitee.com/openeuler/kernel/issues/I4S8HA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8e34d07dd4d9f7811d8ae35adee24e78a4576844 -------------------------------- commit 1ade48d0c27d5da1ccf4b583d8c5fc8b534a3ac8 upstream. The existing cleanup routine implementation is not well synchronized with the syscall routine. When a device is detaching, below race could occur. static int ax25_sendmsg(...) { ... lock_sock() ax25 = sk_to_ax25(sk); if (ax25->ax25_dev == NULL) // CHECK ... ax25_queue_xmit(skb, ax25->ax25_dev->dev); // USE ... } static void ax25_kill_by_device(...) { ... if (s->ax25_dev == ax25_dev) { s->ax25_dev = NULL; ... } Other syscall functions like ax25_getsockopt, ax25_getname, ax25_info_show also suffer from similar races. To fix them, this patch introduce lock_sock() into ax25_kill_by_device in order to guarantee that the nullify action in cleanup routine cannot proceed when another socket request is pending. Signed-off-by: Hanjie Wu Signed-off-by: Lin Ma Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman Signed-off-by: Chen Jun Signed-off-by: Zheng Zengkai --- net/ax25/af_ax25.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index 269ee89d2c2b..22278807b3f3 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -85,8 +85,10 @@ static void ax25_kill_by_device(struct net_device *dev) again: ax25_for_each(s, &ax25_list) { if (s->ax25_dev == ax25_dev) { - s->ax25_dev = NULL; spin_unlock_bh(&ax25_list_lock); + lock_sock(s->sk); + s->ax25_dev = NULL; + release_sock(s->sk); ax25_disconnect(s, ENETUNREACH); spin_lock_bh(&ax25_list_lock); -- GitLab