Patch "sctp: do not peel off an assoc from one netns to another one" has been added to the 3.18-stable tree

Patch "sctp: do not peel off an assoc from one netns to another one" has been added to the 3.18-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

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

to the 3.18-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     sctp-do-not-peel-off-an-assoc-from-one-netns-to-another-one.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Tue Nov 21 15:37:44 CET 2017
From: Xin Long <lucien.xin@gmail.com>
Date: Tue, 17 Oct 2017 23:26:10 +0800
Subject: sctp: do not peel off an assoc from one netns to another one

From: Xin Long <lucien.xin@gmail.com>


[ 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>
---
 net/sctp/socket.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4466,6 +4466,10 @@ int sctp_do_peeloff(struct sock *sk, sct
 	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;
+
 	if (!asoc)
 		return -EINVAL;
 


Patches currently in stable-queue which might be from lucien.xin@gmail.com are

queue-3.18/sctp-do-not-peel-off-an-assoc-from-one-netns-to-another-one.patch