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Subject[PATCH 3.10 249/250] dccp/tcp: do not inherit mc_list from parent
Date
From: Eric Dumazet <edumazet@google.com>

commit 657831ffc38e30092a2d5f03d385d710eb88b09a upstream.

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: Willy Tarreau <w@1wt.eu>
---
net/ipv4/inet_connection_sock.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 6acb541..40ac1e2 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -688,6 +688,8 @@ struct sock *inet_csk_clone_lock(const struct sock *sk,
inet_sk(newsk)->inet_sport = inet_rsk(req)->loc_port;
newsk->sk_write_space = sk_stream_write_space;

+ inet_sk(newsk)->mc_list = NULL;
+
newicsk->icsk_retransmits = 0;
newicsk->icsk_backoff = 0;
newicsk->icsk_probes_out = 0;
--
2.8.0.rc2.1.gbe9624a
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