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 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

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-4.4 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 Sun Nov 19 11:12:05 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

commit df80cd9b28b9ebaa284a41df611dbf3a2d05ca74 upstream.

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: Ben Hutchings ben.hutchings@codethink.co.uk 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 @@ -4453,6 +4453,10 @@ 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-4.4/sctp-do-not-peel-off-an-assoc-from-one-netns-to-another-one.patch