Описание
In the Linux kernel, the following vulnerability has been resolved:
tracing: Undo the registration when enabling the histogram trigger fails
Commit 6f86bdeab633 ("tracing: Fix bad hist from corrupting named_triggers
list") described how a trigger that is registered but not on file->triggers
ends up freed while still on the global named_triggers list, and moved the
registration down so that hist_trigger_enable() follows it immediately. One
path still gets there. hist_trigger_enable() adds the trigger and takes it
straight back out when the event cannot be enabled:
list_add_tail_rcu(&data->list, &file->triggers);
update_cond_flag(file);
if (trace_event_trigger_enable_disable(file, 1) < 0) {
list_del_rcu(&data->list);
update_cond_flag(file);
ret--;
}
so the list walk in hist_unregister_trigger() matches nothing, test stays
NULL, and the ->free() that would call del_named_trigger() is skipped.
out_unreg falls through to out_free, which frees the trigger anyway:
BUG: KASAN: slab-use-after-free in find_named_trigger+0xac/0xc0
Read of size 8 at addr ffff8880091d3160 by task init/1
find_named_trigger+0xac/0xc0
hist_register_trigger+0xc1/0xa00
event_hist_trigger_parse+0x3146/0x6af0
event_trigger_write+0xce/0x160
Freed by task 69:
kfree+0x154/0x420
trigger_kthread_fn+0xfd/0x160
Leave the trigger where hist_unregister_trigger() can find it and let that
undo the registration, which is the only code that knows all of what
cmd_ops->init() took: the named list entry, the hist_pad reference, the
reference on the trigger a named histogram is shared with, and the copied
cmd_ops. It also pairs the failed trace_event_trigger_enable_disable(),
whose sm_ref and buffered event reference are otherwise left behind.
Since ->free() releases trigger_data and, for a trigger that does not share
its histogram, hist_data with it, out_unreg can no longer fall through to
out_free. For a trigger that does share, hist_register_trigger() has
already destroyed the caller's hist_data, so the fall-through was reading
freed memory there as well.
Move the enable_timestamps check in hist_unregister_trigger() above the
->free() call for the same reason: hist_data does not outlive it once the
trigger being removed is the one that owns it.
A flaw was found in the Linux kernel's tracing subsystem. When enabling a histogram event trigger fails, improper registration cleanup can leave an already freed trigger referenced on an internal tracking list. A local attacker with permission to configure event tracing could exploit this flaw to cause a use-after-free condition, leading to a system crash and Denial of Service (DoS) or potential privilege escalation.
Отчет
A use-after-free flaw was found in the Linux kernel's tracing subsystem histogram trigger implementation (kernel/trace/trace_events_hist.c), which Red Hat rates as Moderate impact. When enabling a histogram event trigger fails, the error path removes the trigger from the per-file trigger list before the normal unregistration processing runs, so the cleanup code cannot find it and skips removing its entry from the global named_triggers list; the trigger is then freed while still referenced there. Subsequent trigger operations, such as find_named_trigger(), can dereference that freed memory (KASAN reports a slab-use-after-free read), most likely crashing the kernel and causing a denial of service. Exploiting this flaw requires local access with the privileges needed to configure event tracing through tracefs, typically root or CAP_SYS_ADMIN. Because the confirmed impact is a read of freed memory by an already-privileged local user and no arbitrary memory write has been demonstrated, Red Hat assesses this as a denial-of-service issue (CVSS 3.1 score 5.5, AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H), lower in practical severity than the upstream description's mention of potential privilege escalation. Red Hat Enterprise Linux 6 and 7 are not affected because the vulnerable code is not present in those releases. For the affected Red Hat Enterprise Linux 8, 9, and 10, Red Hat In-Vehicle OS, and OpenShift Container Platform (RHEL CoreOS) streams, the fix is deferred: since only users who already hold administrative privileges on the system can trigger the flaw and the primary consequence is a kernel crash, the fix will be delivered in a future scheduled update rather than an immediate erratum. The residual risk is therefore limited to denial of service by an already-privileged local user.
Меры по смягчению последствий
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 6 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Fix deferred | ||
| Red Hat Enterprise Linux 9 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Fix deferred | ||
| Red Hat OpenShift Container Platform 4 | openshift/ose-rhel-coreos-8 | Fix deferred | ||
| Red Hat OpenShift Container Platform 4 | openshift/ose-rhel-coreos-9 | Fix deferred |
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Дополнительная информация
Статус:
EPSS
5.5 Medium
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: tracing: Undo the registration when enabling the histogram trigger fails Commit 6f86bdeab633 ("tracing: Fix bad hist from corrupting named_triggers list") described how a trigger that is registered but not on file->triggers ends up freed while still on the global named_triggers list, and moved the registration down so that hist_trigger_enable() follows it immediately. One path still gets there. hist_trigger_enable() adds the trigger and takes it straight back out when the event cannot be enabled: list_add_tail_rcu(&data->list, &file->triggers); update_cond_flag(file); if (trace_event_trigger_enable_disable(file, 1) < 0) { list_del_rcu(&data->list); update_cond_flag(file); ret--; } so the list walk in hist_unregister_trigger() matches nothing, test stays NULL, and the ->free() that would call del_named_trigger() is skipped. out_unreg falls through to out_free, which frees the trigger anyway: BUG: KASAN: slab-use-afte...
In the Linux kernel, the following vulnerability has been resolved: tracing: Undo the registration when enabling the histogram trigger fails Commit 6f86bdeab633 ("tracing: Fix bad hist from corrupting named_triggers list") described how a trigger that is registered but not on file->triggers ends up freed while still on the global named_triggers list, and moved the registration down so that hist_trigger_enable() follows it immediately. One path still gets there. hist_trigger_enable() adds the trigger and takes it straight back out when the event cannot be enabled: list_add_tail_rcu(&data->list, &file->triggers); update_cond_flag(file); if (trace_event_trigger_enable_disable(file, 1) < 0) { list_del_rcu(&data->list); update_cond_flag(file); ret--; } so the list walk in hist_unregister_trigger() matches nothing, test stays NULL, and the ->free() that would call del_named_trigger() is skipped. out_unreg falls through to out_free, which frees the trigger anyway: BUG: KASAN
tracing: Undo the registration when enabling the histogram trigger fails
In the Linux kernel, the following vulnerability has been resolved: t ...
In the Linux kernel, the following vulnerability has been resolved: tracing: Undo the registration when enabling the histogram trigger fails Commit 6f86bdeab633 ("tracing: Fix bad hist from corrupting named_triggers list") described how a trigger that is registered but not on file->triggers ends up freed while still on the global named_triggers list, and moved the registration down so that hist_trigger_enable() follows it immediately. One path still gets there. hist_trigger_enable() adds the trigger and takes it straight back out when the event cannot be enabled: list_add_tail_rcu(&data->list, &file->triggers); update_cond_flag(file); if (trace_event_trigger_enable_disable(file, 1) < 0) { list_del_rcu(&data->list); update_cond_flag(file); ret--; } so the list walk in hist_unregister_trigger() matches nothing, test stays NULL, and the ->free() that would call del_named_trigger() is skipped. out_unreg falls through to out_free, which frees the trigger anyway: BUG: KA...
EPSS
5.5 Medium
CVSS3