CVE-2024-40945 in Linux
Summary
by MITRE • 07/12/2024
In the Linux kernel, the following vulnerability has been resolved:
iommu: Return right value in iommu_sva_bind_device()
iommu_sva_bind_device() should return either a sva bond handle or an ERR_PTR value in error cases. Existing drivers (idxd and uacce) only check the return value with IS_ERR(). This could potentially lead to a kernel NULL pointer dereference issue if the function returns NULL instead of an error pointer.
In reality, this doesn't cause any problems because iommu_sva_bind_device() only returns NULL when the kernel is not configured with CONFIG_IOMMU_SVA. In this case, iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA) will return an error, and the device drivers won't call iommu_sva_bind_device() at all.
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Analysis
by VulDB Data Team • 02/21/2025
The vulnerability described in CVE-2024-40945 pertains to a potential null pointer dereference issue within the Linux kernel's IOMMU subsystem, specifically in the iommu_sva_bind_device() function. This function serves a critical role in managing shared virtual addressing (SVA) bindings between devices and the IOMMU system, which is fundamental to modern memory management and security architectures in virtualized environments. The issue arises from an inconsistency in the return value handling of this function, creating a potential pathway for kernel-level exploitation when certain conditions are met.
The technical flaw manifests in the improper return value handling of the iommu_sva_bind_device() function, which should consistently return either a valid SVA bond handle or an ERR_PTR value in error scenarios according to standard kernel programming practices. However, under specific circumstances, the function may return NULL instead of an appropriate error pointer, creating a scenario where downstream drivers that only check return values using IS_ERR() could inadvertently attempt to dereference a NULL pointer. This inconsistency violates the established kernel coding conventions and creates a potential attack surface for privilege escalation or system instability.
The operational impact of this vulnerability extends beyond simple kernel crashes, as it represents a potential security weakness in the IOMMU subsystem that could be exploited by malicious actors to gain unauthorized access to system resources. While the vulnerability is mitigated by the fact that iommu_sva_bind_device() only returns NULL when the kernel lacks CONFIG_IOMMU_SVA configuration, this does not eliminate the risk entirely. The issue becomes particularly concerning in environments where kernel configuration options may be manipulated or where the security model relies on the assumption that all kernel functions behave predictably. The vulnerability affects drivers such as idxd and uacce, which are part of the Intel Data Center Acceleration (IDX) and Universal Acceleration (UACCE) subsystems, highlighting the broader implications for hardware acceleration and virtualization technologies.
The mitigation approach for this vulnerability focuses on ensuring consistent return value handling within the iommu_sva_bind_device() function, requiring that it always returns either a valid handle or an appropriate error pointer rather than NULL in error conditions. This aligns with the Common Weakness Enumeration (CWE) category CWE-476 which addresses NULL Pointer Dereference issues, and corresponds to ATT&CK technique T1068 which involves local privilege escalation through kernel vulnerabilities. System administrators should ensure that kernel configurations properly enforce IOMMU SVA support and that all affected drivers are updated to handle return values correctly. The vulnerability demonstrates the importance of maintaining consistent error handling patterns in kernel code and underscores the need for rigorous code review processes to prevent such subtle but potentially critical issues in security-critical subsystems.