UBUNTU-CVE-2026-72154: Low severity ubuntu/linux-hwe-edge vulnerability
In the Linux kernel, the following vulnerability has been resolved: openrisc: Fix jumplabel smp syncing The original commit 8c30b0018f9d ("openrisc: Add jump label support") copies from arm64 and does not properly consider how icache invalidation on remote cores works in OpenRISC. On OpenRISC remote icaches need to be invalidated otherwise static key's may remain state after updating. Fix SMP cache syncing by: 1. Properly invalidate remote core icaches on SMP systems by using icacheallinv. The old code uses kickallcpussync() which runs a no-op IPI function call on remote CPU's which does execute a lot of code and flushes many cache lines in the process, but does not flush all and it's not correct on OpenRISC. 2. For architectures that do not have WRITETHROUGH caches be sure to flush the dcache after patching. To test this I first reproduced the issue using a custom test module [0]. The test confirmed that some icache lines maintained stale statickey code sequences after calling staticbranchenable(). After this patch there are no longer jumplabel coherency issues. [0] https://github.com/stffrdhrn/or1k-utils/tree/master/tests/smpstatickeytest
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
ubuntu/linux-aws-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14~24.04.1 - Upgrade
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ubuntu/linux-azure-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17~24.04.1 - Upgrade
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ubuntu/linux-azure-fde-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1016.16~24.04.1 - Upgrade
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ubuntu/linux-gcp-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14~24.04.1 - Upgrade
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ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-38.38~24.04.4 - Upgrade
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ubuntu/linux-nvidia-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1024.25~24.04.1 - Upgrade
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ubuntu/linux-oracle-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1013.13~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1~24.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-38.38 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 7.0.0-1016.16 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 7.0.0-1008.9 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1015.15 - Upgrade
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ubuntu/linux-nvidia-bosto a version that resolves this vulnerability.Fixed in 7.0.0-2022.23 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1015.15 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Upgrade
Upgrade
ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Compensating control
On OpenRISC SMP systems, invalidate remote CPU instruction caches after updating static keys by using icache_all_inv.
- Compensating control
On architectures without write-through caches, flush the data cache after patching.
Event History
Frequently Asked Questions
Which systems are realistically affected by this issue?
The underlying flaw is in the OpenRISC jump-label implementation and concerns instruction-cache synchronization across remote CPUs on SMP systems. It is relevant where OpenRISC SMP systems update static keys or jump labels at runtime.
What conditions are needed to trigger the problem?
A local, low-privileged attacker would need the ability to cause runtime static-key or jump-label updates on an affected OpenRISC SMP kernel. The reported failure occurs when remote CPU instruction caches retain stale static-key code sequences after static_branch_enable().
How can the issue be recognized in testing or investigation?
The described symptom is stale static-key code remaining in remote-core instruction-cache lines after a static-key update. A custom SMP static-key test module was used to reproduce the condition before the fix.
What does the fix change?
The fix invalidates remote-core instruction caches on SMP systems using icache_all_inv rather than relying on kick_all_cpus_sync(). It also flushes the data cache after patching on architectures without write-through caches.