From: Eric Dumazet <edumazet@google.com>
Date: Tue, 9 May 2017 13:29:19 +0000 (-0700)
Subject: dccp/tcp: do not inherit mc_list from parent
X-Git-Tag: v4.1.12-106.0.20170710_2300~58
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=f9d78e8b329f15d7d4ddc64c9a56c257770acc73;p=users%2Fjedix%2Flinux-maple.git

dccp/tcp: do not inherit mc_list from parent

Orabug: 26408144
CVE: CVE-2017-8890

syzkaller found a way to trigger double frees from ip_mc_drop_socket()

It turns out that leave a copy of parent mc_list at accept() time,
which is very bad.

Very similar to commit 8b485ce69876 ("tcp: do not inherit
fastopen_req from parent")

Initial report from Pray3r, completed by Andrey one.
Thanks a lot to them !

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Pray3r <pray3r.z@gmail.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Brian Maly <brian.maly@oracle.com>

Conflicts:
	net/ipv4/inet_connection_sock.c
---

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 4d2bc8c6694f..11a8a8486137 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -719,6 +719,8 @@ struct sock *inet_csk_clone_lock(const struct sock *sk,
 		inet_sk(newsk)->inet_sport = htons(inet_rsk(req)->ir_num);
 		newsk->sk_write_space = sk_stream_write_space;
 
+		inet_sk(newsk)->mc_list = NULL;
+
 		newsk->sk_mark = inet_rsk(req)->ir_mark;
 		atomic64_set(&newsk->sk_cookie,
 			     atomic64_read(&inet_rsk(req)->ir_cookie));