CVE-2024-26937 in Linux
Summary
by MITRE • 05/01/2024
In the Linux kernel, the following vulnerability has been resolved:
drm/i915/gt: Reset queue_priority_hint on parking
Originally, with strict in order execution, we could complete execution only when the queue was empty. Preempt-to-busy allows replacement of an active request that may complete before the preemption is processed by HW. If that happens, the request is retired from the queue, but the queue_priority_hint remains set, preventing direct submission until after the next CS interrupt is processed.
This preempt-to-busy race can be triggered by the heartbeat, which will also act as the power-management barrier and upon completion allow us to idle the HW. We may process the completion of the heartbeat, and begin parking the engine before the CS event that restores the queue_priority_hint, causing us to fail the assertion that it is MIN.
<3>[ 166.210729] __engine_park:283 GEM_BUG_ON(engine->sched_engine->queue_priority_hint != (-((int)(~0U >> 1)) - 1))
<0>[ 166.210781] Dumping ftrace buffer:
<0>[ 166.210795] ---------------------------------
... <0>[ 167.302811] drm_fdin-1097 2..s1. 165741070us : trace_ports: 0000:00:02.0 rcs0: promote { ccid:20 1217:2 prio 0 }
<0>[ 167.302861] drm_fdin-1097 2d.s2. 165741072us : execlists_submission_tasklet: 0000:00:02.0 rcs0: preempting last=1217:2, prio=0, hint=2147483646
<0>[ 167.302928] drm_fdin-1097 2d.s2. 165741072us : __i915_request_unsubmit: 0000:00:02.0 rcs0: fence 1217:2, current 0
<0>[ 167.302992] drm_fdin-1097 2d.s2. 165741073us : __i915_request_submit: 0000:00:02.0 rcs0: fence 3:4660, current 4659
<0>[ 167.303044] drm_fdin-1097 2d.s1. 165741076us : execlists_submission_tasklet: 0000:00:02.0 rcs0: context:3 schedule-in, ccid:40
<0>[ 167.303095] drm_fdin-1097 2d.s1. 165741077us : trace_ports: 0000:00:02.0 rcs0: submit { ccid:40 3:4660* prio 2147483646 }
<0>[ 167.303159] kworker/-89 11..... 165741139us : i915_request_retire.part.0: 0000:00:02.0 rcs0: fence c90:2, current 2
<0>[ 167.303208] kworker/-89 11..... 165741148us : __intel_context_do_unpin: 0000:00:02.0 rcs0: context:c90 unpin
<0>[ 167.303272] kworker/-89 11..... 165741159us : i915_request_retire.part.0: 0000:00:02.0 rcs0: fence 1217:2, current 2
<0>[ 167.303321] kworker/-89 11..... 165741166us : __intel_context_do_unpin: 0000:00:02.0 rcs0: context:1217 unpin
<0>[ 167.303384] kworker/-89 11..... 165741170us : i915_request_retire.part.0: 0000:00:02.0 rcs0: fence 3:4660, current 4660
<0>[ 167.303434] kworker/-89 11d..1. 165741172us : __intel_context_retire: 0000:00:02.0 rcs0: context:1216 retire runtime: { total:56028ns, avg:56028ns }
<0>[ 167.303484] kworker/-89 11..... 165741198us : __engine_park: 0000:00:02.0 rcs0: parked
<0>[ 167.303534] <idle>-0 5d.H3. 165741207us : execlists_irq_handler: 0000:00:02.0 rcs0: semaphore yield: 00000040
<0>[ 167.303583] kworker/-89 11..... 165741397us : __intel_context_retire: 0000:00:02.0 rcs0: context:1217 retire runtime: { total:325575ns, avg:0ns }
<0>[ 167.303756] kworker/-89 11..... 165741777us : __intel_context_retire: 0000:00:02.0 rcs0: context:c90 retire runtime: { total:0ns, avg:0ns }
<0>[ 167.303806] kworker/-89 11..... 165742017us : __engine_park: __engine_park:283 GEM_BUG_ON(engine->sched_engine->queue_priority_hint != (-((int)(~0U >> 1)) - 1))
<0>[ 167.303811] ---------------------------------
<4>[ 167.304722] ------------[ cut here ]------------
<2>[ 167.304725] kernel BUG at drivers/gpu/drm/i915/gt/intel_engine_pm.c:283!
<4>[ 167.304731] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
<4>[ 167.304734] CPU: 11 PID: 89 Comm: kworker/11:1 Tainted: G W 6.8.0-rc2-CI_DRM_14193-gc655e0fd2804+ #1
<4>[ 167.304736] Hardware name: Intel Corporation Rocket Lake Client Platform/RocketLake S UDIMM 6L RVP, BIOS RKLSFWI1.R00.3173.A03.2204210138 04/21/2022
<4>[ 167.304738] Workqueue: i915-unordered retire_work_handler [i915]
<4>[ 16
---truncated---
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Analysis
by VulDB Data Team • 01/26/2026
The vulnerability CVE-2024-26937 resides within the Linux kernel's graphics driver component, specifically in the intel i915 driver responsible for managing Intel GPU hardware. This issue manifests as a race condition during the execution of graphics workloads, particularly when preempt-to-busy functionality is involved. The flaw occurs in the drm/i915/gt subsystem where the queue_priority_hint variable is not properly reset during engine parking operations, leading to a kernel BUG and system crash. The root cause stems from the interaction between hardware preemption mechanisms and software scheduling logic, where an active request can be preempted and retired before the hardware preemption process completes, leaving the queue_priority_hint in an inconsistent state. This inconsistency causes the engine parking function to fail its assertion check, which validates that the queue_priority_hint must be set to a specific minimum value, triggering a kernel panic.
The technical flaw involves a complex interplay between GPU scheduling, preemption, and power management mechanisms within the Intel graphics driver. When a heartbeat operation is performed as part of power management, it acts as a barrier that can trigger the engine parking sequence before the hardware completion event that would normally reset the queue_priority_hint. This race condition is particularly evident in systems using strict in-order execution with preempt-to-busy capabilities, where the timing of request retirement and hardware event processing creates a window where the software state becomes inconsistent with the hardware state. The kernel log traces show a clear sequence of events where a request is preempted, retired, and then the engine parking attempt fails due to the corrupted queue_priority_hint value, which is expected to be the minimum possible integer value but instead retains a large positive value from the preemption process.
The operational impact of this vulnerability is severe as it can lead to complete system crashes and kernel panics, particularly in environments that rely heavily on GPU workloads and power management features. Systems running the affected Linux kernel versions with Intel graphics hardware are at risk of experiencing unexpected reboots or system hangs when graphics workloads are submitted concurrently with power management operations. This vulnerability affects graphics-intensive applications, gaming platforms, and any system where the i915 driver is actively managing GPU resources, potentially causing data loss and service interruptions. The crash occurs during the engine parking phase, which is a critical part of the GPU's power management cycle, making it particularly problematic for laptop systems and mobile devices that depend on efficient power management for battery life.
Mitigation strategies for CVE-2024-26937 primarily involve updating to a patched Linux kernel version that resolves the race condition in the intel i915 driver. System administrators should prioritize applying the latest kernel updates from their distribution vendors or directly from the Linux kernel mainline. Additionally, monitoring for kernel panic logs related to queue_priority_hint assertions can help identify systems that may be vulnerable before they experience a crash. For environments where immediate updates are not feasible, implementing runtime monitoring and automated restart procedures can help maintain system availability. The fix implemented in the patched kernel ensures that the queue_priority_hint is properly reset during the engine parking process, eliminating the race condition that leads to the assertion failure. This vulnerability aligns with CWE-362, which describes a race condition in concurrent programming, and may be categorized under ATT&CK technique T1489, which involves system shutdown/reboot to disrupt services, though the impact here is more subtle as a system crash rather than intentional disruption.