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References: <20220928002741.64237-1-kuniyu@amazon.com> <20220928002741.64237-4-kuniyu@amazon.com>
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From:   Eric Dumazet <edumazet@google.com>
Date:   Tue, 27 Sep 2022 20:43:51 -0700
Message-ID: <CANn89iL00_Gz+jiczvmHPCV9nO7Lzctq_JLyp1V-0obuPWBanQ@mail.gmail.com>
Subject: Re: [PATCH v2 net 3/5] tcp/udp: Call inet6_destroy_sock() in IPv6 sk->sk_destruct().
To:     Kuniyuki Iwashima <kuniyu@amazon.com>
Cc:     "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        David Ahern <dsahern@kernel.org>,
        Kuniyuki Iwashima <kuni1840@gmail.com>,
        netdev <netdev@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        LKML <linux-kernel@vger.kernel.org>
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On Tue, Sep 27, 2022 at 5:29 PM Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
>
> Originally, inet6_sk(sk)->XXX were changed under lock_sock(), so we were
> able to clean them up by calling inet6_destroy_sock() during the IPv6 ->
> IPv4 conversion by IPV6_ADDRFORM.  However, commit 03485f2adcde ("udpv6:
> Add lockless sendmsg() support") added a lockless memory allocation path,
> which could cause a memory leak:
>
> setsockopt(IPV6_ADDRFORM)                 sendmsg()
> +-----------------------+                 +-------+
> - do_ipv6_setsockopt(sk, ...)             - udpv6_sendmsg(sk, ...)
>   - lock_sock(sk)                           ^._ called via udpv6_prot
>   - WRITE_ONCE(sk->sk_prot, &tcp_prot)          before WRITE_ONCE()
>   - inet6_destroy_sock()
>   - release_sock(sk)                        - ip6_make_skb(sk, ...)
>                                               ^._ lockless fast path for
>                                                   the non-corking case
>
>                                               - __ip6_append_data(sk, ...)
>                                                 - ipv6_local_rxpmtu(sk, ...)
>                                                   - xchg(&np->rxpmtu, skb)
>                                                     ^._ rxpmtu is never freed.
>
>                                             - lock_sock(sk)
>
> For now, rxpmtu is only the case, but let's call inet6_destroy_sock()
> in IPv6 sk->sk_destruct() not to miss the future change and a similar
> bug fixed in commit e27326009a3d ("net: ping6: Fix memleak in
> ipv6_renew_options().")

I do not see how your patches prevent rxpmtu to be created at the time
of IPV6_ADDRFROM ?

There seem to be races.

lockless UDP sendmsg() is a disaster really.

>
> We can now remove all inet6_destroy_sock() calls from IPv6 protocol
> specific ->destroy() functions, but such changes are invasive to
> backport.  So they can be posted as a follow-up later for net-next.
>
> Fixes: 03485f2adcde ("udpv6: Add lockless sendmsg() support")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> ---
>  include/net/ipv6.h  |  1 +
>  include/net/udp.h   |  2 +-
>  net/ipv4/udp.c      |  8 ++++++--
>  net/ipv6/af_inet6.c |  9 ++++++++-
>  net/ipv6/udp.c      | 15 ++++++++++++++-
>  5 files changed, 30 insertions(+), 5 deletions(-)
>
> diff --git a/include/net/ipv6.h b/include/net/ipv6.h
> index de9dcc5652c4..11f1a9a8b066 100644
> --- a/include/net/ipv6.h
> +++ b/include/net/ipv6.h
> @@ -1178,6 +1178,7 @@ void ipv6_icmp_error(struct sock *sk, struct sk_buff *skb, int err, __be16 port,
>  void ipv6_local_error(struct sock *sk, int err, struct flowi6 *fl6, u32 info);
>  void ipv6_local_rxpmtu(struct sock *sk, struct flowi6 *fl6, u32 mtu);
>
> +void inet6_sock_destruct(struct sock *sk);
>  int inet6_release(struct socket *sock);
>  int inet6_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len);
>  int inet6_getname(struct socket *sock, struct sockaddr *uaddr,
> diff --git a/include/net/udp.h b/include/net/udp.h
> index 5ee88ddf79c3..fee053bcd17c 100644
> --- a/include/net/udp.h
> +++ b/include/net/udp.h
> @@ -247,7 +247,7 @@ static inline bool udp_sk_bound_dev_eq(struct net *net, int bound_dev_if,
>  }
>
>  /* net/ipv4/udp.c */
> -void udp_destruct_sock(struct sock *sk);
> +void udp_destruct_common(struct sock *sk);
>  void skb_consume_udp(struct sock *sk, struct sk_buff *skb, int len);
>  int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb);
>  void udp_skb_destructor(struct sock *sk, struct sk_buff *skb);
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index 560d9eadeaa5..a84ae44db7e2 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -1598,7 +1598,7 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
>  }
>  EXPORT_SYMBOL_GPL(__udp_enqueue_schedule_skb);
>
> -void udp_destruct_sock(struct sock *sk)
> +void udp_destruct_common(struct sock *sk)
>  {
>         /* reclaim completely the forward allocated memory */
>         struct udp_sock *up = udp_sk(sk);
> @@ -1611,10 +1611,14 @@ void udp_destruct_sock(struct sock *sk)
>                 kfree_skb(skb);
>         }
>         udp_rmem_release(sk, total, 0, true);
> +}
> +EXPORT_SYMBOL_GPL(udp_destruct_common);
>
> +static void udp_destruct_sock(struct sock *sk)
> +{
> +       udp_destruct_common(sk);
>         inet_sock_destruct(sk);
>  }
> -EXPORT_SYMBOL_GPL(udp_destruct_sock);
>
>  int udp_init_sock(struct sock *sk)
>  {
> diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
> index dbb1430d6cc2..0774cff62f2d 100644
> --- a/net/ipv6/af_inet6.c
> +++ b/net/ipv6/af_inet6.c
> @@ -109,6 +109,13 @@ static __inline__ struct ipv6_pinfo *inet6_sk_generic(struct sock *sk)
>         return (struct ipv6_pinfo *)(((u8 *)sk) + offset);
>  }
>
> +void inet6_sock_destruct(struct sock *sk)
> +{
> +       inet6_destroy_sock(sk);
> +       inet_sock_destruct(sk);
> +}
> +EXPORT_SYMBOL_GPL(inet6_sock_destruct);
> +
>  static int inet6_create(struct net *net, struct socket *sock, int protocol,
>                         int kern)
>  {
> @@ -201,7 +208,7 @@ static int inet6_create(struct net *net, struct socket *sock, int protocol,
>                         inet->hdrincl = 1;
>         }
>
> -       sk->sk_destruct         = inet_sock_destruct;
> +       sk->sk_destruct         = inet6_sock_destruct;
>         sk->sk_family           = PF_INET6;
>         sk->sk_protocol         = protocol;
>
> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
> index 3366d6a77ff2..a5256f7184ab 100644
> --- a/net/ipv6/udp.c
> +++ b/net/ipv6/udp.c
> @@ -56,6 +56,19 @@
>  #include <trace/events/skb.h>
>  #include "udp_impl.h"
>
> +static void udpv6_destruct_sock(struct sock *sk)
> +{
> +       udp_destruct_common(sk);
> +       inet6_sock_destruct(sk);
> +}
> +
> +static int udpv6_init_sock(struct sock *sk)
> +{
> +       skb_queue_head_init(&udp_sk(sk)->reader_queue);
> +       sk->sk_destruct = udpv6_destruct_sock;
> +       return 0;
> +}
> +
>  static u32 udp6_ehashfn(const struct net *net,
>                         const struct in6_addr *laddr,
>                         const u16 lport,
> @@ -1723,7 +1736,7 @@ struct proto udpv6_prot = {
>         .connect                = ip6_datagram_connect,
>         .disconnect             = udp_disconnect,
>         .ioctl                  = udp_ioctl,
> -       .init                   = udp_init_sock,
> +       .init                   = udpv6_init_sock,
>         .destroy                = udpv6_destroy_sock,
>         .setsockopt             = udpv6_setsockopt,
>         .getsockopt             = udpv6_getsockopt,
> --
> 2.30.2
>