tree 1044bd2be0b259ddffdfb49394cde75ede3e6caa
parent 1afe78e4c6298120cbcebabfc9137bf3dc8dcfdc
author Jordan Rife <jrife@google.com> 1692654323 -0500
committer COS Cherry Picker <cloud-image-release@prod.google.com> 1694216414 -0700

net: Avoid address overwrite in kernel_connect

BPF programs that run on connect can rewrite the connect address. For
the connect system call this isn't a problem, because a copy of the address
is made when it is moved into kernel space. However, kernel_connect
simply passes through the address it is given, so the caller may observe
its address value unexpectedly change.

A practical example where this is problematic is where NFS is combined
with a system such as Cilium which implements BPF-based load balancing.
A common pattern in software-defined storage systems is to have an NFS
mount that connects to a persistent virtual IP which in turn maps to an
ephemeral server IP. This is usually done to achieve high availability:
if your server goes down you can quickly spin up a replacement and remap
the virtual IP to that endpoint. With BPF-based load balancing, mounts
will forget the virtual IP address when the address rewrite occurs
because a pointer to the only copy of that address is passed down the
stack. Server failover then breaks, because clients have forgotten the
virtual IP address. Reconnects fail and mounts remain broken. This patch
was tested by setting up a scenario like this and ensuring that NFS
reconnects worked after applying the patch.

BUG=b/294602647
TEST=presubmit
RELEASE_NOTE=Fixes problem with NFS reconnects when using DPv2 in
kube-proxy-free mode.

cos-patch: bug
Change-Id: I2f47461d2cbf7aafbadfb148d7c612cb6b7589c1
Signed-off-by: Jordan Rife <jrife@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 0bdf399342c5acbd817c9098b6c7ed21f1974312)
Signed-off-by: Chenglong Tang <chenglongtang@google.com>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/56889
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Main-Branch-Verified: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Robert Kolchmeyer <rkolchmeyer@google.com>