From: Arnd Bergmann <arnd@arndb.de>
Date: Tue, 22 Mar 2011 01:18:00 +0000 (-0700)
Subject: net/appletalk: fix atalk_release use after free
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=b20e7bbfc7a15a4182730f0936433145992b4b06;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git

net/appletalk: fix atalk_release use after free

The BKL removal in appletalk introduced a use-after-free problem,
where atalk_destroy_socket frees a sock, but we still release
the socket lock on it.

An easy fix is to take an extra reference on the sock and sock_put
it when returning from atalk_release.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/appletalk/ddp.c b/net/appletalk/ddp.c
index 3d4f4b043406..206e771e82d1 100644
--- a/net/appletalk/ddp.c
+++ b/net/appletalk/ddp.c
@@ -1051,6 +1051,7 @@ static int atalk_release(struct socket *sock)
 {
 	struct sock *sk = sock->sk;
 
+	sock_hold(sk);
 	lock_sock(sk);
 	if (sk) {
 		sock_orphan(sk);
@@ -1058,6 +1059,8 @@ static int atalk_release(struct socket *sock)
 		atalk_destroy_socket(sk);
 	}
 	release_sock(sk);
+	sock_put(sk);
+
 	return 0;
 }