In the Linux kernel, the following vulnerability has been resolved:
powerpc/qspinlock: Fix deadlock in MCS queue
If an interrupt occurs in queued_spin_lock_slowpath() after we increment qnodesp->count and before node->lock is initialized, another CPU might see stale lock values in get_tail_qnode(). If the stale lock value happens to match the lock on that CPU, then we write to the "next" pointer of the wrong qnode. This causes a deadlock as the former CPU, once it becomes the head of the MCS queue, will spin indefinitely until it's "next" pointer is set by its successor in the queue.
Running stress-ng on a 16 core (16EC/16VP) shared LPAR, results in occasional lockups similar to the following:
$ stress-ng --all 128 --vm-bytes 80% --aggressive \ --maximize --oomable --verify --syslog \ --metrics --times --timeout 5m
watchdog: CPU 15 Hard LOCKUP ...... NIP [c0000000000b78f4] queued_spin_lock_slowpath+0x1184/0x1490 LR [c000000001037c5c] _raw_spin_lock+0x6c/0x90 Call Trace: 0xc000002cfffa3bf0 (unreliable) _raw_spin_lock+0x6c/0x90 raw_spin_rq_lock_nested.part.135+0x4c/0xd0 sched_ttwu_pending+0x60/0x1f0 __flush_smp_call_function_queue+0x1dc/0x670 smp_ipi_demux_relaxed+0xa4/0x100 xive_muxed_ipi_action+0x20/0x40 __handle_irq_event_percpu+0x80/0x240 handle_irq_event_percpu+0x2c/0x80 handle_percpu_irq+0x84/0xd0 generic_handle_irq+0x54/0x80 __do_irq+0xac/0x210 __do_IRQ+0x74/0xd0 0x0 do_IRQ+0x8c/0x170 hardware_interrupt_common_virt+0x29c/0x2a0 --- interrupt: 500 at queued_spin_lock_slowpath+0x4b8/0x1490 ...... NIP [c0000000000b6c28] queued_spin_lock_slowpath+0x4b8/0x1490 LR [c000000001037c5c] _raw_spin_lock+0x6c/0x90 --- interrupt: 500 0xc0000029c1a41d00 (unreliable) _raw_spin_lock+0x6c/0x90 futex_wake+0x100/0x260 do_futex+0x21c/0x2a0 sys_futex+0x98/0x270 system_call_exception+0x14c/0x2f0 system_call_vectored_common+0x15c/0x2ec
The following code flow illustrates how the deadlock occurs. For the sake of brevity, assume that both locks (A and B) are contended and we call the queued_spin_lock_slowpath() function.
CPU0 CPU1 ---- ---- spin_lock_irqsave(A) | spin_unlock_irqrestore(A) | spin_lock(B) | | | ▼ | id = qnodesp->count++; | (Note that nodes[0].lock == A) | | | ▼ | Interrupt | (happens before "nodes[0].lock = B") | | | ▼ | spin_lock_irqsave(A) | | | ▼ | id = qnodesp->count++ | nodes[1].lock = A | | | ▼ | Tail of MCS queue | | spin_lock_irqsave(A) ▼ | Head of MCS queue ▼ | CPU0 is previous tail ▼ | Spin indefinitely ▼ (until "nodes[1].next != NULL") prev = get_tail_qnode(A, CPU0) | ▼ prev == &qnodes[CPU0].nodes[0] (as qnodes ---truncated---
CVSS Details
- CVSS 3.1 Base Score: 5.5
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Debian | — | Upgrade linux | Jul 27, 2026 | Jul 27, 2026 |
| Redhat_linux | — | No solution exists | Jul 9, 2025 | Sep 18, 2024 |
| Suse | — | Upgrade kernel-obs-buildUpgrade ocfs2-kmp-rtUpgrade dtb-lgUpgrade kernel-develUpgrade dtb-caviumUpgrade dtb-mediatekUpgrade dtb-qcomUpgrade dtb-exynosUpgrade reiserfs-kmp-azureUpgrade kselftests-kmp-64kbUpgrade ocfs2-kmp-defaultUpgrade dlm-kmp-64kbUpgrade dtb-alteraUpgrade kernel-rtUpgrade kernel-rt-develUpgrade dtb-rockchipUpgrade kernel-sourceUpgrade dtb-allwinnerUpgrade kernel-kvmsmallUpgrade kernel-syms-azureUpgrade dtb-xilinxUpgrade kernel-azure-livepatch-develUpgrade dtb-nvidiaUpgrade kernel-default-vdsoUpgrade kernel-devel-azureUpgrade cluster-md-kmp-rtUpgrade kernel-kvmsmall-develUpgrade gfs2-kmp-rtUpgrade kernel-source-azureUpgrade kernel-64kb-develUpgrade kernel-default-optionalUpgrade gfs2-kmp-defaultUpgrade kernel-devel-rtUpgrade kernel-default-base-rebuildUpgrade dtb-armUpgrade kernel-zfcpdumpUpgrade kernel-source-vanillaUpgrade kernel-rt-extraUpgrade cluster-md-kmp-azureUpgrade kernel-azure-optionalUpgrade kernel-azure-develUpgrade ocfs2-kmp-azureUpgrade gfs2-kmp-azureUpgrade kernel-rt_debug-develUpgrade kernel-rt_debug-livepatch-develUpgrade kselftests-kmp-azureUpgrade kernel-64kb-optionalUpgrade kselftests-kmp-defaultUpgrade kernel-default-extraUpgrade kernel-symsUpgrade kernel-rt-livepatch-develUpgrade kernel-kvmsmall-vdsoUpgrade kernel-docsUpgrade dtb-broadcomUpgrade reiserfs-kmp-defaultUpgrade reiserfs-kmp-64kbUpgrade kernel-debug-livepatch-develUpgrade cluster-md-kmp-defaultUpgrade kernel-debug-develUpgrade kernel-macrosUpgrade kernel-debugUpgrade kernel-azure-vdsoUpgrade dlm-kmp-defaultUpgrade kernel-rt-optionalUpgrade kernel-default-baseUpgrade kernel-64kbUpgrade kernel-defaultUpgrade kernel-azure-extraUpgrade kernel-syms-rtUpgrade kernel-azureUpgrade dtb-apmUpgrade kselftests-kmp-rtUpgrade kernel-rt-vdsoUpgrade kernel-obs-qaUpgrade kernel-default-livepatchUpgrade dtb-socionextUpgrade dtb-marvellUpgrade dtb-amlogicUpgrade reiserfs-kmp-rtUpgrade dtb-amazonUpgrade kernel-default-livepatch-develUpgrade cluster-md-kmp-64kbUpgrade dtb-renesasUpgrade kernel-rt_debugUpgrade kernel-kvmsmall-livepatch-develUpgrade kernel-64kb-extraUpgrade dtb-sprdUpgrade ocfs2-kmp-64kbUpgrade kernel-debug-vdsoUpgrade gfs2-kmp-64kbUpgrade dlm-kmp-rtUpgrade kernel-default-develUpgrade dtb-hisiliconUpgrade dtb-freescaleUpgrade dtb-appleUpgrade dtb-amdUpgrade dlm-kmp-azureUpgrade kernel-64kb-livepatch-develUpgrade kernel-source-rtUpgrade kernel-rt_debug-vdsoUpgrade kernel-docs-html | Dec 5, 2025 | Oct 8, 2024 |
| Ubuntu | — | Upgrade linux-image-oracleUpgrade linux-image-gcpUpgrade linux-image-6.8.0-1017-oracle-64kUpgrade linux-image-ibm-classicUpgrade linux-image-azureUpgrade linux-image-generic-hwe-22.04Upgrade linux-image-6.8.0-1017-ibmUpgrade linux-image-6.8.0-50-lowlatencyUpgrade linux-image-awsUpgrade linux-image-azure-fdeUpgrade linux-image-lowlatency-64k-hwe-24.04Upgrade linux-image-6.8.0-1019-nvidia-lowlatencyUpgrade linux-image-nvidia-64k-6.8Upgrade linux-image-generic-hwe-24.04Upgrade linux-image-ibm-lts-24.04Upgrade linux-image-6.8.0-1002-gkeopUpgrade linux-image-nvidia-64kUpgrade linux-image-6.8.0-50-lowlatency-64kUpgrade linux-image-oem-22.04bUpgrade linux-image-oem-22.04aUpgrade linux-image-gkeop-6.8Upgrade linux-image-nvidia-lowlatencyUpgrade linux-image-oem-24.04aUpgrade linux-image-generic-64k-hwe-24.04Upgrade linux-image-kvmUpgrade linux-image-lowlatency-hwe-22.04Upgrade linux-image-6.8.0-1016-raspiUpgrade linux-image-6.8.0-1019-gcpUpgrade linux-image-oracle-64kUpgrade linux-image-nvidia-lowlatency-64kUpgrade linux-image-raspiUpgrade linux-image-6.8.0-1019-nvidia-64kUpgrade linux-image-6.8.0-1020-azure-fdeUpgrade linux-image-6.8.0-50-genericUpgrade linux-image-ibmUpgrade linux-image-oem-22.04cUpgrade linux-image-generic-64kUpgrade linux-image-virtualUpgrade linux-image-genericUpgrade linux-image-6.8.0-1019-nvidia-lowlatency-64kUpgrade linux-image-6.8.0-1015-gkeUpgrade linux-image-nvidiaUpgrade linux-image-virtual-hwe-22.04Upgrade linux-image-generic-lpaeUpgrade linux-image-gkeopUpgrade linux-image-6.8.0-1019-nvidiaUpgrade linux-image-oem-24.04Upgrade linux-image-6.8.0-1020-azureUpgrade linux-image-virtual-hwe-24.04Upgrade linux-image-lowlatencyUpgrade linux-image-6.8.0-1017-oracleUpgrade linux-image-oem-22.04Upgrade linux-image-6.8.0-1020-awsUpgrade linux-image-generic-64k-hwe-22.04Upgrade linux-image-lowlatency-64k-hwe-22.04Upgrade linux-image-oem-22.04dUpgrade linux-image-6.8.0-1018-oemUpgrade linux-image-lowlatency-64kUpgrade linux-image-nvidia-hwe-22.04Upgrade linux-image-nvidia-6.8Upgrade linux-image-nvidia-64k-hwe-22.04Upgrade linux-image-gkeUpgrade linux-image-lowlatency-hwe-24.04Upgrade linux-image-6.8.0-50-generic-64k | Dec 13, 2024 | Sep 18, 2024 |
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