CVE-2025-38275 in Linux
Summary
by MITRE • 07/10/2025
In the Linux kernel, the following vulnerability has been resolved:
phy: qcom-qmp-usb: Fix an NULL vs IS_ERR() bug
The qmp_usb_iomap() helper function currently returns the raw result of devm_ioremap() for non-exclusive mappings. Since devm_ioremap() may return a NULL pointer and the caller only checks error pointers with IS_ERR(), NULL could bypass the check and lead to an invalid dereference.
Fix the issue by checking if devm_ioremap() returns NULL. When it does, qmp_usb_iomap() now returns an error pointer via IOMEM_ERR_PTR(-ENOMEM), ensuring safe and consistent error handling.
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Analysis
by VulDB Data Team • 12/19/2025
The vulnerability identified as CVE-2025-38275 resides within the Linux kernel's phy driver for Qualcomm QMP USB controllers, specifically affecting the qcom-qmp-usb subsystem. This issue represents a critical flaw in error handling mechanisms that could potentially lead to system instability or privilege escalation. The vulnerability stems from improper handling of memory mapping operations within the USB phy driver, creating a scenario where null pointer dereferences could occur during device initialization or operation. The affected component operates at the kernel level, making it particularly dangerous as it could be exploited to compromise system integrity or availability.
The technical flaw manifests in the qmp_usb_iomap() helper function which directly returns the result of devm_ioremap() without proper validation. The devm_ioremap() function is designed to map device memory regions into kernel virtual address space, but it can return NULL pointers when memory allocation fails. The current implementation fails to check for this NULL return value, relying solely on IS_ERR() macro which only evaluates error pointers, not null pointers. This creates a dangerous race condition where a NULL return from devm_ioremap() bypasses all error checking mechanisms and gets passed to subsequent code paths, resulting in invalid memory dereferences. This type of vulnerability falls under CWE-476 which specifically addresses NULL pointer dereference issues in software development, and represents a classic example of improper error handling in kernel space operations.
The operational impact of this vulnerability extends beyond simple system crashes, potentially enabling malicious actors to exploit the NULL vs IS_ERR() bug for privilege escalation or denial of service attacks. When a USB controller is initialized or reconfigured, the faulty code path could cause kernel panics, system hangs, or more concerning, allow attackers to manipulate kernel memory structures through crafted USB device interactions. The vulnerability is particularly concerning in embedded systems or mobile devices where USB functionality is frequently used and where kernel-level exploits could lead to complete system compromise. This aligns with ATT&CK technique T1068 which involves exploiting legitimate credentials and privileges to gain system access, as the vulnerability could be leveraged to escalate privileges within the kernel space.
The fix implemented addresses the core issue by introducing explicit NULL pointer checking within the qmp_usb_iomap() function. When devm_ioremap() returns NULL, the function now properly converts this to an error pointer using IOMEM_ERR_PTR(-ENOMEM) which ensures consistent error handling throughout the kernel subsystem. This approach maintains compatibility with existing error checking mechanisms that rely on IS_ERR() macro while preventing the dangerous NULL pointer propagation. The solution follows established kernel development practices for memory mapping error handling and ensures that all memory allocation failures are properly reported and handled. The mitigation strategy effectively closes the vulnerability window by ensuring that no null pointer can bypass the error handling chain, thereby preventing invalid memory dereferences that could lead to system crashes or exploitation. This fix demonstrates proper adherence to kernel security principles and represents a robust solution that maintains system stability while preserving the intended functionality of the USB phy driver.