Ubuntu 24.04
6.8.0-79-generic
Based on my tests, it seems at least in this one scenario, the memory
exhaustion appears to happen if/when the auditd userspace service
is installed and enabled. Apparmor had no bearing on the problem as it I had it
disabled:
With Auditd ENABLED and apparmor DISABLED:
====================================
lab@leaktest:~$ sudo aa-status
apparmor module is loaded.
apparmor filesystem is not mounted.
lab@leaktest:~$ sudo s^C
lab@leaktest:~$ cat /proc/cmdline
BOOT_IMAGE=/vmlinuz-6.8.0-79-generic
root=UUID=d36f7414-beb7-45e0-900e-9ab79cdbcb2d ro console=tty1 console=ttyS0
apparmor=0
Auditd rate limiting noted in logs:
---
[Wed Sep 3 17:58:59 2025] audit: rate limit exceeded
[Wed Sep 3 17:59:00 2025] audit: audit_lost=289836 audit_rate_limit=100
audit_backlog_limit=8192
[Wed Sep 3 17:59:00 2025] audit: rate limit exceeded
[Wed Sep 3 17:59:01 2025] audit: audit_lost=292814 audit_rate_limit=100
audit_backlog_limit=8192
[Wed Sep 3 17:59:01 2025] audit: rate limit exceeded
Memory usage ballooned from ~ 500MB to 1.7GB (would continue to the host max
6GB before OOM'ing), slabtop output:
---
Active / Total Objects (% used) : 1698488 / 1700387 (99.9%)
Active / Total Slabs (% used) : 93380 / 93380 (100.0%)
Active / Total Caches (% used) : 322 / 382 (84.3%)
Active / Total Size (% used) : 1599014.75K / 1600024.15K (99.9%)
Minimum / Average / Maximum Object : 0.01K / 0.94K / 10.25K
OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
676976 676976 100% 2.00K 42311 16 1353952K kmalloc-rnd-01-2k
677104 677104 100% 0.25K 42319 16 169276K skbuff_head_cache
With both Auditd DISABLED and apparmor DISABLED:
====================================
lab@leaktest:~$ sudo systemctl status auditd.service
○ auditd.service
Loaded: masked (Reason: Unit auditd.service is masked.)
Active: inactive (dead)
lab@leaktest:~$ cat /proc/cmdline
BOOT_IMAGE=/vmlinuz-6.8.0-79-generic
root=UUID=d36f7414-beb7-45e0-900e-9ab79cdbcb2d ro console=tty1 console=ttyS0
apparmor=0
Memory usage maintained at around 350-400M
slabtop:
---
Active / Total Objects (% used) : 347603 / 348988 (99.6%)
Active / Total Slabs (% used) : 8876 / 8876 (100.0%)
Active / Total Caches (% used) : 325 / 382 (85.1%)
Active / Total Size (% used) : 75899.81K / 76508.71K (99.2%)
Minimum / Average / Maximum Object : 0.01K / 0.22K / 10.25K
OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
10650 10650 100% 0.62K 426 25 6816K inode_cache
39648 39648 100% 0.14K 1416 28 5664K kernfs_node_cache
4536 4536 100% 1.16K 168 27 5376K ext4_inode_cache
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https://bugs.launchpad.net/bugs/2098730
Title:
Kernel 6.8.0 memory leak
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