linux-kernel - [PATCH net] kcm: Fix use-after-free caused by clonned sockets

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Date:   Fri, 1 Jun 2018 14:30:38 +0300
From:   Kirill Tkhai <ktkhai@...tuozzo.com>
To:     "David S. Miller" <davem@...emloft.net>, ebiggers@...gle.com,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, tom@...ntonium.net,
        viro@...IV.linux.org.uk, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net] kcm: Fix use-after-free caused by clonned sockets

(resend for properly queueing in patchwork)

kcm_clone() creates kernel socket, which does not take net counter.
Thus, the net may die before the socket is completely destructed,
i.e. kcm_exit_net() is executed before kcm_done().

Reported-by: syzbot+5f1a04e374a635efc426@...kaller.appspotmail.com
Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>
---
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index d67734c99027..84b7d5c6fec8 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -1671,7 +1671,7 @@ static struct file *kcm_clone(struct socket *osock)
 	__module_get(newsock->ops->owner);
 
 	newsk = sk_alloc(sock_net(osock->sk), PF_KCM, GFP_KERNEL,
-			 &kcm_proto, true);
+			 &kcm_proto, false);
 	if (!newsk) {
 		sock_release(newsock);
 		return ERR_PTR(-ENOMEM);