linux-kernel - [PATCH 4.4 02/53] dccp/tcp: do not inherit mc

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Message-Id: <20170605153037.201779820@linuxfoundation.org>
Date:   Mon,  5 Jun 2017 18:17:00 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        Pray3r <pray3r.z@...il.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.4 02/53] dccp/tcp: do not inherit mc_list from parent

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@...gle.com>


[ Upstream commit 657831ffc38e30092a2d5f03d385d710eb88b09a ]

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@...gle.com>
Reported-by: Pray3r <pray3r.z@...il.com>
Reported-by: Andrey Konovalov <andreyknvl@...gle.com>
Tested-by: Andrey Konovalov <andreyknvl@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/inet_connection_sock.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -669,6 +669,8 @@ struct sock *inet_csk_clone_lock(const s
 		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));