CVE-2023-54045

In the Linux kernel, the following vulnerability has been resolved:

audit: fix possible soft lockup in __audit_inode_child()

Tracefs or debugfs maybe cause hundreds to thousands of PATH records, too many PATH records maybe cause soft lockup.

For example:

1. CONFIG_KASAN=y && CONFIG_PREEMPTION=n
2. auditctl -a exit,always -S open -k key
3. sysctl -w kernel.watchdog_thresh=5
4. mkdir /sys/kernel/debug/tracing/instances/test

There may be a soft lockup as follows: watchdog: BUG: soft lockup - CPU#45 stuck for 7s! [mkdir:15498] Kernel panic - not syncing: softlockup: hung tasks Call trace: dump_backtrace+0x0/0x30c show_stack+0x20/0x30 dump_stack+0x11c/0x174 panic+0x27c/0x494 watchdog_timer_fn+0x2bc/0x390 __run_hrtimer+0x148/0x4fc __hrtimer_run_queues+0x154/0x210 hrtimer_interrupt+0x2c4/0x760 arch_timer_handler_phys+0x48/0x60 handle_percpu_devid_irq+0xe0/0x340 __handle_domain_irq+0xbc/0x130 gic_handle_irq+0x78/0x460 el1_irq+0xb8/0x140 __audit_inode_child+0x240/0x7bc tracefs_create_file+0x1b8/0x2a0 trace_create_file+0x18/0x50 event_create_dir+0x204/0x30c __trace_add_new_event+0xac/0x100 event_trace_add_tracer+0xa0/0x130 trace_array_create_dir+0x60/0x140 trace_array_create+0x1e0/0x370 instance_mkdir+0x90/0xd0 tracefs_syscall_mkdir+0x68/0xa0 vfs_mkdir+0x21c/0x34c do_mkdirat+0x1b4/0x1d4 __arm64_sys_mkdirat+0x4c/0x60 el0_svc_common.constprop.0+0xa8/0x240 do_el0_svc+0x8c/0xc0 el0_svc+0x20/0x30 el0_sync_handler+0xb0/0xb4 el0_sync+0x160/0x180

Therefore, we add cond_resched() to __audit_inode_child() to fix it.

A denial of service condition exists in the Linux audit subsystem because __audit_inode_child can run for a long time when it must process very large numbers of audit name entries and generate many PATH records. In configurations without kernel preemption such as CONFIG_PREEMPTION disabled and with an aggressive watchdog threshold, this long non reschedulable execution can cause a soft lockup report and may lead to a forced kernel panic due to the watchdog. A practical trigger is to enable auditing for relevant syscalls and then perform filesystem operations that create paths producing hundreds or thousands of PATH audit records. The example involves creating a tracefs instance directory which causes extensive path processing and eventually stalls a CPU long enough to trip the watchdog.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.