CVE-2024-36887 in Linux
Summary
by MITRE • 05/30/2024
In the Linux kernel, the following vulnerability has been resolved:
e1000e: change usleep_range to udelay in PHY mdic access
This is a partial revert of commit 6dbdd4de0362 ("e1000e: Workaround for sporadic MDI error on Meteor Lake systems"). The referenced commit used usleep_range inside the PHY access routines, which are sometimes called from an atomic context. This can lead to a kernel panic in some scenarios, such as cable disconnection and reconnection on vPro systems.
Solve this by changing the usleep_range calls back to udelay.
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Analysis
by VulDB Data Team • 08/28/2025
The vulnerability CVE-2024-36887 affects the Linux kernel's e1000e network driver implementation, specifically addressing a critical issue in PHY management interface access routines. This flaw manifests in systems utilizing Intel Meteor Lake processors with vPro capabilities, where the driver's handling of MDI (Media Dependent Interface) operations creates a potential for system instability. The root cause stems from improper timing mechanisms within the driver's atomic context execution environment, leading to kernel panic conditions during normal network cable operations. The vulnerability impacts network reliability and system stability in enterprise and workstation environments where these specific hardware configurations are deployed.
The technical flaw involves a problematic transition from udelay to usleep_range function calls within the PHY access routines of the e1000e driver. When the driver attempts to access PHY registers during network cable disconnection and reconnection events, it executes these operations from atomic contexts where certain kernel functions are prohibited or highly restricted. The usleep_range function, while providing more precise timing control, is incompatible with atomic execution contexts and can cause kernel panics when invoked in such scenarios. This creates a direct violation of kernel execution constraints where atomic operations must not block or sleep, making the use of usleep_range inappropriately disruptive to system stability.
The operational impact of this vulnerability extends beyond simple network connectivity issues to potentially causing complete system crashes in affected environments. When users disconnect and reconnect network cables on systems equipped with Intel Meteor Lake processors and vPro features, the kernel may panic and require system reboot. This represents a significant reliability concern for enterprise deployments where network connectivity is critical and unexpected system reboots can cause productivity loss and data integrity concerns. The vulnerability affects systems where the e1000e driver is actively managing network interfaces, particularly in scenarios involving dynamic network configuration changes and hardware event handling.
The mitigation strategy involves reverting to the previous implementation that utilized udelay instead of usleep_range within the PHY access routines, effectively addressing the atomic context incompatibility. This partial revert of commit 6dbdd4de0362 restores proper timing mechanisms that are compatible with kernel atomic execution requirements while maintaining the intended workaround for MDI errors on Meteor Lake systems. The solution maintains the original intent of addressing sporadic MDI errors while eliminating the kernel panic conditions that occurred during normal cable operations. This remediation aligns with best practices for kernel driver development where timing functions must be carefully selected based on execution context requirements, and represents a standard approach to resolving atomic context violations in kernel modules.
This vulnerability demonstrates the importance of proper timing function selection in kernel drivers and highlights the constraints imposed by atomic execution contexts in kernel space operations. The issue relates to CWE-391, which addresses improper handling of kernel execution contexts, and aligns with ATT&CK techniques involving system compromise through kernel-level vulnerabilities. The fix demonstrates the balance between addressing specific hardware workarounds and maintaining system stability under all operational conditions, emphasizing the need for careful consideration of execution context requirements in kernel module development.