Merge branch 'vsock-test-check-for-null-ptr-deref-when-transport-changes'

Luigi Leonardi says:

====================
vsock/test: check for null-ptr-deref when transport changes

This series introduces a new test that checks for a null pointer
dereference that may happen when there is a transport change[1]. This
bug was fixed in [2].

Note that this test *cannot* fail, it hangs if it triggers a kernel
oops. The intended use-case is to run it and then check if there is any
oops in the dmesg.

This test is based on Hyunwoo Kim's[3] and Michal's python
reproducers[4].

[1]https://lore.kernel.org/netdev/Z2LvdTTQR7dBmPb5@v4bel-B760M-AORUS-ELITE-AX/
[2]https://lore.kernel.org/netdev/20250110083511.30419-1-sgarzare@redhat.com/
[3]https://lore.kernel.org/netdev/Z2LvdTTQR7dBmPb5@v4bel-B760M-AORUS-ELITE-AX/#t
[4]https://lore.kernel.org/netdev/2b3062e3-bdaa-4c94-a3c0-2930595b9670@rbox.co/

v4: https://lore.kernel.org/20250624-test_vsock-v4-1-087c9c8e25a2@redhat.com
v3: https://lore.kernel.org/20250611-test_vsock-v3-1-8414a2d4df62@redhat.com
v2: https://lore.kernel.org/20250314-test_vsock-v2-1-3c0a1d878a6d@redhat.com
v1: https://lore.kernel.org/20250306-test_vsock-v1-0-0320b5accf92@redhat.com
====================

Link: https://patch.msgid.link/20250630-test_vsock-v5-0-2492e141e80b@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>