openvswitch: fix soft lockup in the netlink flow dump

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-99025
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-23 13:17:25 UTC
Updated2026-10-23 13:17:25 UTC
DescriptionIn 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 63e7959c4b9bd6f791061c460a22d9ee32ae2240 c995c52eba1926a5e82823fa5573a6f1b1010e5d git Not specified
CNA Linux Linux affected 63e7959c4b9bd6f791061c460a22d9ee32ae2240 b872de585edff534056c65ba30970b68499fca14 git Not specified
CNA Linux Linux affected 63e7959c4b9bd6f791061c460a22d9ee32ae2240 55f12552b00a34ca7ab5cf2d2b5ed02f8f06a965 git Not specified
CNA Linux Linux affected 63e7959c4b9bd6f791061c460a22d9ee32ae2240 80db24f3c16fdeef85460d9d66a4aae7a9cb92b4 git Not specified
CNA Linux Linux affected 63e7959c4b9bd6f791061c460a22d9ee32ae2240 aaaaf87ea99b8766c9a8aa0e71aa42e6bc8a5320 git Not specified
CNA Linux Linux affected 3.16 Not specified
CNA Linux Linux unaffected 3.16 semver Not specified
CNA Linux Linux unaffected 6.6.160 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.113 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.57 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.11 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/80db24f3c16fdeef85460d9d66a4aae7a9cb92b4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/aaaaf87ea99b8766c9a8aa0e71aa42e6bc8a5320 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/55f12552b00a34ca7ab5cf2d2b5ed02f8f06a965 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c995c52eba1926a5e82823fa5573a6f1b1010e5d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b872de585edff534056c65ba30970b68499fca14 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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