On Tue, May 9, 2017 at 6:29 AM, Eric Dumazet <eric.duma...@gmail.com> wrote:
> From: Eric Dumazet <eduma...@google.com>
>
> 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 <eduma...@google.com>
> Reported-by: Pray3r <pray3...@gmail.com>
> Reported-by: Andrey Konovalov <andreyk...@google.com>
> Tested-by: Andrey Konovalov <andreyk...@google.com>
> ---
> v2: fix moved into inet_csk_clone_lock() to fix both DCCP and TCP
>
> 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
> 5e313c1ac94fc88eca5fe3a0e9e46e551e955ff0..1054d330bf9df3189a21dbb08e27c0e6ad136775
> 100644
> --- a/net/ipv4/inet_connection_sock.c
> +++ b/net/ipv4/inet_connection_sock.c
> @@ -794,6 +794,8 @@ struct sock *inet_csk_clone_lock(const struct sock *sk,
> /* listeners have SOCK_RCU_FREE, not the children */
> sock_reset_flag(newsk, SOCK_RCU_FREE);
>
> + 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));
>
I think IPv6 needs this too?
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index aeb9497..b3611d9 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1062,6 +1062,7 @@ static struct sock *tcp_v6_syn_recv_sock(const
struct sock *sk, struct sk_buff *
newtp->af_specific = &tcp_sock_ipv6_mapped_specific;
#endif
+ newnp->ipv6_mc_list = NULL;
newnp->ipv6_ac_list = NULL;
newnp->ipv6_fl_list = NULL;
newnp->pktoptions = NULL;
