Описание
In the Linux kernel, the following vulnerability has been resolved:
openvswitch: fix soft lockup in the netlink flow dump
A production compute node carrying a few thousand datapath flows hit a
soft lockup inside a single netlink flow dump and panicked.
ovs_flow_cmd_dump() calls ovs_flow_stats_get() for every flow it
emits, and that releases stats->lock with spin_unlock_bh() once per
CPU that has touched the flow. Every release is a local_bh_enable(),
and each one runs the pending softirq backlog in the dumping thread's
own context.
The skb bounds the flows one callback emits, but not the softirq work
it absorbs. On a CPU that carries the box's packet load the backlog
refills as fast as it drains, so the dumping thread becomes that CPU's
softirq engine. It never sleeps and it has no reschedule point, so
under voluntary preemption nothing can take the CPU away from it:
neither the ksoftirqd the kernel woke to take the work over, nor the
stopper thread the softlockup detector dispatches to refresh its
timestamp.
Hold BH off across the whole callback instead, the way
ctnetlink_dump_table() does, so the nested spin_unlock_bh() stop
draining softirqs. The loop already runs under rcu_read_lock() and
cannot sleep. What it gives up is preemption under CONFIG_PREEMPT,
since a BH-off region is not preemptible outside PREEMPT_RT. The
region stays short: the skb caps the flows one callback emits, and
empty buckets cost no skb space but are each visited once per dump, as
the cursor only moves forward. The table grows on insert and shrinks
only on flush, so the walk is bounded by the largest flow count the
datapath has held. The softirq backlog the callback used to absorb has
no bound at all.
A flaw was found in the Linux kernel's Open vSwitch component. A local attacker can cause a Denial of Service (DoS) by initiating a Netlink flow dump while the system is processing heavy network traffic. In this scenario, the dumping thread repeatedly processes pending software interrupts without yielding CPU execution time, triggering a kernel soft lockup and subsequent system crash.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 6 | kernel | Out of support scope | ||
| Red Hat Enterprise Linux 7 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Fix deferred | ||
| 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
4.7 Medium
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: openvswitch: fix soft lockup in the netlink flow dump A production compute node carrying a few thousand datapath flows hit a soft lockup inside a single netlink flow dump and panicked. ovs_flow_cmd_dump() calls ovs_flow_stats_get() for every flow it emits, and that releases stats->lock with spin_unlock_bh() once per CPU that has touched the flow. Every release is a local_bh_enable(), and each one runs the pending softirq backlog in the dumping thread's own context. The skb bounds the flows one callback emits, but not the softirq work it absorbs. On a CPU that carries the box's packet load the backlog refills as fast as it drains, so the dumping thread becomes that CPU's softirq engine. It never sleeps and it has no reschedule point, so under voluntary preemption nothing can take the CPU away from it: neither the ksoftirqd the kernel woke to take the work over, nor the stopper thread the softlockup detector dispatche...
In the Linux kernel, the following vulnerability has been resolved: openvswitch: fix soft lockup in the netlink flow dump A production compute node carrying a few thousand datapath flows hit a soft lockup inside a single netlink flow dump and panicked. ovs_flow_cmd_dump() calls ovs_flow_stats_get() for every flow it emits, and that releases stats->lock with spin_unlock_bh() once per CPU that has touched the flow. Every release is a local_bh_enable(), and each one runs the pending softirq backlog in the dumping thread's own context. The skb bounds the flows one callback emits, but not the softirq work it absorbs. On a CPU that carries the box's packet load the backlog refills as fast as it drains, so the dumping thread becomes that CPU's softirq engine. It never sleeps and it has no reschedule point, so under voluntary preemption nothing can take the CPU away from it: neither the ksoftirqd the kernel woke to take the work over, nor the stopper thread the softlockup detector dispatch
In the Linux kernel, the following vulnerability has been resolved: o ...
In the Linux kernel, the following vulnerability has been resolved: openvswitch: fix soft lockup in the netlink flow dump A production compute node carrying a few thousand datapath flows hit a soft lockup inside a single netlink flow dump and panicked. ovs_flow_cmd_dump() calls ovs_flow_stats_get() for every flow it emits, and that releases stats->lock with spin_unlock_bh() once per CPU that has touched the flow. Every release is a local_bh_enable(), and each one runs the pending softirq backlog in the dumping thread's own context. The skb bounds the flows one callback emits, but not the softirq work it absorbs. On a CPU that carries the box's packet load the backlog refills as fast as it drains, so the dumping thread becomes that CPU's softirq engine. It never sleeps and it has no reschedule point, so under voluntary preemption nothing can take the CPU away from it: neither the ksoftirqd the kernel woke to take the work over, nor the stopper thread the softlockup detector dispa...
EPSS
4.7 Medium
CVSS3