CVE-2026-23470: Linux Kernel DRM Imagination DoS Flaw

CVE-2026-23470 Overview

A deadlock vulnerability has been identified in the Linux kernel's DRM/Imagination graphics driver. The flaw exists within the soft reset sequence implementation, where disable_irq() is improperly called from a threaded IRQ handler. Since disable_irq() internally waits for IRQ handlers to complete, calling it from within the handler itself creates a deadlock condition where the handler waits for itself to finish.

Critical Impact

System deadlock can occur during soft reset operations in the Imagination GPU driver, potentially causing system hangs and denial of service conditions.

Affected Products

• Linux Kernel with DRM/Imagination driver enabled
• Systems utilizing Imagination Technologies GPU hardware
• Embedded devices and platforms using PowerVR-based graphics

Discovery Timeline

• April 3, 2026 - CVE CVE-2026-23470 published to NVD
• April 7, 2026 - Last updated in NVD database

Technical Details for CVE-2026-23470

Vulnerability Analysis

The vulnerability occurs in the DRM subsystem's Imagination graphics driver during the soft reset sequence. The problematic code path involves calling disable_irq() from within a threaded IRQ handler context. The disable_irq() function is designed to synchronously disable an interrupt line and wait for any currently executing handlers to complete before returning. When this function is called from within the handler itself, it creates a circular wait condition—the handler cannot complete because it's waiting for itself to finish.

This deadlock scenario results in a complete system hang as the IRQ handling thread becomes permanently blocked. The impact is particularly significant for systems relying on Imagination Technologies GPUs, as any GPU operation triggering a soft reset would cause the entire system to become unresponsive.

Root Cause

The root cause is an improper synchronization mechanism in the soft reset code path. The developer originally used disable_irq() to ensure interrupt safety during the reset sequence, but failed to account for the execution context being within the threaded IRQ handler. The fix involves replacing disable_irq() with disable_irq_nosync(), which disables the interrupt without waiting for handlers to complete, thus avoiding the self-deadlock condition.

Attack Vector

This vulnerability has an unknown attack vector based on current analysis. While the deadlock condition is primarily triggered through normal driver operation during GPU soft reset scenarios, the potential for malicious exploitation exists:

An attacker with local access could potentially craft GPU workloads or trigger conditions that force repeated soft resets, leading to systematic denial of service. The vulnerability requires the ability to interact with the GPU driver, which may be possible through graphics APIs or direct device access depending on system configuration.

Detection Methods for CVE-2026-23470

Indicators of Compromise

• System hangs or freezes during GPU-intensive operations
• Unresponsive systems following Imagination GPU driver initialization or reset
• Kernel soft lockup warnings related to the DRM/Imagination driver
• IRQ handler stack traces showing blocking waits on disable_irq() calls

Detection Strategies

• Monitor kernel logs for soft lockup warnings involving the Imagination DRM driver
• Track system availability metrics for unexpected hangs on systems with PowerVR GPUs
• Implement watchdog monitoring to detect and recover from deadlock conditions
• Review kernel panic dumps for IRQ handler deadlock patterns

Monitoring Recommendations

• Enable kernel lockup detectors (CONFIG_SOFTLOCKUP_DETECTOR) to identify blocking conditions
• Configure system monitoring to alert on GPU driver-related kernel warnings
• Implement automated system health checks for embedded platforms using Imagination GPUs
• Review dmesg output regularly for DRM subsystem error messages

How to Mitigate CVE-2026-23470

Immediate Actions Required

• Update to a patched Linux kernel version containing the fix
• If immediate patching is not possible, consider disabling the Imagination GPU driver temporarily
• Schedule maintenance windows for kernel updates on affected systems
• Back up system configurations before applying kernel patches

Patch Information

The Linux kernel maintainers have released patches to address this vulnerability. The fix replaces the problematic disable_irq() call with disable_irq_nosync() during the soft reset sequence, allowing the interrupt to be disabled without waiting for the current handler to complete.

Patches are available through the following kernel git commits:

• Kernel Git Commit 6f39b48
• Kernel Git Commit 9497b1f
• Kernel Git Commit a55c2a5
• Kernel Git Commit f99e8b8

Workarounds

• Disable the Imagination DRM driver via kernel boot parameter modprobe.blacklist=imagination_drm
• Use alternative GPU drivers where available on affected platforms
• Implement hardware watchdog timers to recover from potential deadlock conditions
• Consider reverting to a previous stable kernel version if patched versions are not yet available

# Configuration example
# To blacklist the Imagination DRM driver until a patched kernel is available:
echo "blacklist imagination_drm" >> /etc/modprobe.d/blacklist.conf

# Rebuild initramfs to apply changes
update-initramfs -u

# Verify driver is not loaded after reboot
lsmod | grep imagination