hi Matthew,
I did some investigation in 5.15.0-66-generic,  lsm_multiple_contexts()return 0 
that make audit_log_lsm() return without malloc memory thus avoiding memory 
leaks.

audit_log_lsm()
->if (!lsm_multiple_contexts())
        return;

I haven't found out which commit change the behavior of
lsm_multiple_contexts().

Jianlin

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https://bugs.launchpad.net/bugs/1987430

Title:
  Ubuntu 22.04 kernel 5.15.0-46-generic leaks kernel memory in
  kmalloc-2k slabs

Status in linux package in Ubuntu:
  In Progress
Status in linux source package in Jammy:
  In Progress
Status in linux source package in Kinetic:
  In Progress

Bug description:
  Since updating to kernel 5.15.0-46-generic (package version
  5.15.0-46.49), all of our Ubuntu 22.04 LTS servers are leaking kernel
  memory; our first server with 8 GB of RAM just fatally OOMed, causing
  us to detect this. Inspection of OOM reports, /proc/meminfo, and
  /proc/slabinfo says that it's mostly going to unreclaimable kmalloc-2k
  slabs:

          Aug 23 12:51:11 cluster kernel: [361299.864757] Unreclaimable slab 
info:
          Aug 23 12:51:11 cluster kernel: [361299.864757] Name                  
    Used          Total
          [...]
          Aug 23 12:51:11 cluster kernel: [361299.864924] kmalloc-2k           
6676584KB    6676596KB

  Most of our machines appear to be leaking slab memory at a rate of
  around 20 to 40 Mbytes/hour, with some machines leaking much faster;
  the champions are leaking kernel memory at 145 Mbytes/hour and 237
  Mbytes/hour.

  We aren't running any proprietary kernel modules and our only unusual
  kernel configuration is that we've disabled AppArmor with 'apparmor=0'
  on the kernel command line.

  /proc/version_signature:
  Ubuntu 5.15.0-46.49-generic 5.15.39

  Full kernel command line from the Dell R240 system that fatally OOMd:
  BOOT_IMAGE=/boot/vmlinuz-5.15.0-46-generic 
root=UUID=3165564f-a2dd-4b39-935b-114f3e23ff54 ro console=ttyS0,115200 
console=tty0 apparmor=0

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