I experienced lockups as well. Here's what I found in the logs:
1. AppArmor NULL pointer dereference in __aa_label_next_not_in_set,
called from update_sk_ctx:
Oct 13 12:32:42 ubu kernel: BUG: kernel NULL pointer dereference, address:
000000000000004c
Oct 13 12:32:42 ubu kernel: RIP: 0010:__aa_label_next_not_in_set+0x23/0x100
Oct 13 12:32:42 ubu kernel: Call Trace:
Oct 13 12:32:42 ubu kernel: aa_label_is_subset+0x3f/0x70
Oct 13 12:32:42 ubu kernel: update_sk_ctx+0xfd/0x2c0
Oct 13 12:32:42 ubu kernel: aa_unix_file_perm+0x5c2/0x740
Oct 13 12:32:42 ubu kernel: aa_sock_file_perm+0x91/0xf0
Oct 13 12:32:42 ubu kernel: aa_file_perm+0x36c/0x3b0
Oct 13 12:32:42 ubu kernel: apparmor_file_permission+0x46/0xd0
Oct 13 12:32:42 ubu kernel: security_file_permission+0x5b/0x170
Oct 13 12:32:42 ubu kernel: vfs_write+0x7c/0x490
Oct 13 12:32:42 ubu kernel: ksys_write+0xc6/0xf0
Oct 13 12:32:42 ubu kernel: __x64_sys_write+0x19/0x30
Oct 13 12:32:42 ubu kernel: CPU: 11 PID: 2377512 Comm: systemd.test Tainted: P
O 7.0.0-38-generic
Oct 13 12:32:42 ubu kernel: note: systemd.test[2377512] exited with irqs
disabled
Oct 13 12:32:42 ubu kernel: note: systemd.test[2377512] exited with
preempt_count 1
2. CPU 3 spinning
Oct 13 12:33:06 ubu kernel: watchdog: BUG: soft lockup - CPU#3 stuck for 23s!
[systemd.test:2377526]
Oct 13 12:33:08 ubu kernel: RIP:
0010:native_queued_spin_lock_slowpath+0x7a/0x370
Oct 13 12:33:08 ubu kernel: Call Trace:
Oct 13 12:33:08 ubu kernel: ? _raw_spin_lock+0x3f/0x60
Oct 13 12:33:08 ubu kernel: unix_dgram_poll+0x121/0x1d0
Oct 13 12:33:08 ubu kernel: sock_poll+0x54/0x130
Oct 13 12:33:08 ubu kernel: ep_send_events+0x100/0x2a0
Oct 13 12:33:08 ubu kernel: ep_poll+0x284/0x560
Oct 13 12:33:08 ubu kernel: do_epoll_wait+0x58/0xd0
Oct 13 12:33:08 ubu kernel: __x64_sys_epoll_pwait+0x8c/0x150
3. lockup continues
Oct 13 12:48:10 ubu kernel: watchdog: BUG: soft lockup - CPU#3 stuck for
865s! [systemd.test:2377526]
This was triggered by running snapd unit tests inside of a classic snap (I
don't know which test, but potentially this one or one like it
https://github.com/canonical/snapd/blob/master/systemd/sdnotify_linux_test.go#L161).
I asked an agent to do some digging for me and it tells me that the
issue was introduced with this commit in the kernel:
88fec3526e84123997ecebd6bb6778eb4ce779b7 ("apparmor: make sure unix
socket labeling is correctly updated", merged Jul 20, 2025)
It has been fixed upstream with three commits:
1. 4483efe4f21510b30c24bc97d9fd0e8feab94125 — apparmor: fix shadowing of plabel
that prevents cache from being updated
2. 6d25e7b47616cb2db43351210929c8f19dc305a3 — apparmor: fix refcount leak when
updating the sk_ctx
3. b1aea2c1960771a276d7e68c7424168eccd0c3da — apparmor: fix race in unix socket
mediation when peer_path is used
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https://bugs.launchpad.net/bugs/2170572
Title:
linux-image-7.0.0-38-generic randomly freezes Lenovo Legion 5
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