DLPX-97202 Add esp4/esp6/rxrpc modprobe disable to delphix-platform for CVE-2026-43500 (dirty frag)

[david-mendez1]

Problem

CVE-2026-43500 ("dirty frag") is a critical Linux kernel local privilege
escalation vulnerability (CVSS 7.8, CWE-787) that allows an unprivileged
local user to exploit socket buffers with externally-owned paged fragments
that fall through to in-place decryption paths in the esp4, esp6, and
rxrpc kernel modules.

No upstream kernel fix is available yet for Ubuntu 24.04 LTS — all
Delphix kernel repos still carry the vulnerable code.

Solution

Add /etc/modprobe.d/dirty-frag.conf directly to delphix-platform under
files/common/etc/modprobe.d/, containing:

```
install esp4 /bin/false
install esp6 /bin/false
install rxrpc /bin/false
```

None of these modules are used by the Delphix product. The fix applies to
all platforms (the file lives under files/common/) and blocks the modules
at image build time, independent of which kmod package version is present.

The comment in the file notes that this should be re-evaluated once an
updated kernel containing the upstream fix is deployed.

Testing Done

Verified on an engine that has been setup that these modules are not in loaded (only exist in the kernel).
Manually created file dirty-frag.conf and tried to load the modules:

root@ip-10-110-226-132:/etc/modprobe.d# cat dirty-frag.conf 
install esp4 /bin/false
install esp6 /bin/false
install rxrpc /bin/false
root@ip-10-110-226-132:/etc/modprobe.d# modprobe esp4
modprobe: ERROR: ../libkmod/libkmod-module.c:1084 command_do() Error running install command '/bin/false' for module esp4: retcode 1
modprobe: ERROR: could not insert 'esp4': Invalid argument
root@ip-10-110-226-132:/etc/modprobe.d# modprobe esp6
modprobe: ERROR: ../libkmod/libkmod-module.c:1084 command_do() Error running install command '/bin/false' for module esp6: retcode 1
modprobe: ERROR: could not insert 'esp6': Invalid argument
root@ip-10-110-226-132:/etc/modprobe.d# modprobe rxrpc
modprobe: ERROR: ../libkmod/libkmod-module.c:1084 command_do() Error running install command '/bin/false' for module rxrpc: retcode 1
modprobe: ERROR: could not insert 'rxrpc': Invalid argument

[prakashsurya]

LGTM