sctp: do not peel off an assoc from one netns to another one

[ Upstream commit df80cd9b28b9ebaa284a41df611dbf3a2d05ca74 ]

Now when peeling off an association to the sock in another netns, all
transports in this assoc are not to be rehashed and keep use the old
key in hashtable.

As a transport uses sk->net as the hash key to insert into hashtable,
it would miss removing these transports from hashtable due to the new
netns when closing the sock and all transports are being freeed, then
later an use-after-free issue could be caused when looking up an asoc
and dereferencing those transports.

This is a very old issue since very beginning, ChunYu found it with
syzkaller fuzz testing with this series:

  socket$inet6_sctp()
  bind$inet6()
  sendto$inet6()
  unshare(0x40000000)
  getsockopt$inet_sctp6_SCTP_GET_ASSOC_ID_LIST()
  getsockopt$inet_sctp6_SCTP_SOCKOPT_PEELOFF()

This patch is to block this call when peeling one assoc off from one
netns to another one, so that the netns of all transport would not
go out-sync with the key in hashtable.

Note that this patch didn't fix it by rehashing transports, as it's
difficult to handle the situation when the tuple is already in use
in the new netns. Besides, no one would like to peel off one assoc
to another netns, considering ipaddrs, ifaces, etc. are usually
different.

Reported-by: ChunYu Wang <chunwang@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 7f0f689b8d2b1535708f2facc4932682a45c8bbc..272edd7748a0b96355055edc83d81b8370af0e8e 100644 (file)
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4453,6 +4453,10 @@ int sctp_do_peeloff(struct sock *sk, sctp_assoc_t id, struct socket **sockp)
        struct socket *sock;
        int err = 0;
 
+       /* Do not peel off from one netns to another one. */
+       if (!net_eq(current->nsproxy->net_ns, sock_net(sk)))
+               return -EINVAL;
+
        /* Do not peel off from one netns to another one. */
        if (!net_eq(current->nsproxy->net_ns, sock_net(sk)))
                return -EINVAL;