CVE-2025-38295 in Linux
Summary
by MITRE • 07/10/2025
In the Linux kernel, the following vulnerability has been resolved:
perf/amlogic: Replace smp_processor_id() with raw_smp_processor_id() in meson_ddr_pmu_create()
The Amlogic DDR PMU driver meson_ddr_pmu_create() function incorrectly uses smp_processor_id(), which assumes disabled preemption. This leads to kernel warnings during module loading because meson_ddr_pmu_create() can be called in a preemptible context.
Following kernel warning and stack trace: [ 31.745138] [ T2289] BUG: using smp_processor_id() in preemptible [00000000] code: (udev-worker)/2289
[ 31.745154] [ T2289] caller is debug_smp_processor_id+0x28/0x38
[ 31.745172] [ T2289] CPU: 4 UID: 0 PID: 2289 Comm: (udev-worker) Tainted: GW 6.14.0-0-MANJARO-ARM #1 59519addcbca6ba8de735e151fd7b9e97aac7ff0
[ 31.745181] [ T2289] Tainted: [W]=WARN
[ 31.745183] [ T2289] Hardware name: Hardkernel ODROID-N2Plus (DT)
[ 31.745188] [ T2289] Call trace:
[ 31.745191] [ T2289] show_stack+0x28/0x40 (C)
[ 31.745199] [ T2289] dump_stack_lvl+0x4c/0x198
[ 31.745205] [ T2289] dump_stack+0x20/0x50
[ 31.745209] [ T2289] check_preemption_disabled+0xec/0xf0
[ 31.745213] [ T2289] debug_smp_processor_id+0x28/0x38
[ 31.745216] [ T2289] meson_ddr_pmu_create+0x200/0x560 [meson_ddr_pmu_g12 8095101c49676ad138d9961e3eddaee10acca7bd]
[ 31.745237] [ T2289] g12_ddr_pmu_probe+0x20/0x38 [meson_ddr_pmu_g12 8095101c49676ad138d9961e3eddaee10acca7bd]
[ 31.745246] [ T2289] platform_probe+0x98/0xe0
[ 31.745254] [ T2289] really_probe+0x144/0x3f8
[ 31.745258] [ T2289] __driver_probe_device+0xb8/0x180
[ 31.745261] [ T2289] driver_probe_device+0x54/0x268
[ 31.745264] [ T2289] __driver_attach+0x11c/0x288
[ 31.745267] [ T2289] bus_for_each_dev+0xfc/0x160
[ 31.745274] [ T2289] driver_attach+0x34/0x50
[ 31.745277] [ T2289] bus_add_driver+0x160/0x2b0
[ 31.745281] [ T2289] driver_register+0x78/0x120
[ 31.745285] [ T2289] __platform_driver_register+0x30/0x48
[ 31.745288] [ T2289] init_module+0x30/0xfe0 [meson_ddr_pmu_g12 8095101c49676ad138d9961e3eddaee10acca7bd]
[ 31.745298] [ T2289] do_one_initcall+0x11c/0x438
[ 31.745303] [ T2289] do_init_module+0x68/0x228
[ 31.745311] [ T2289] load_module+0x118c/0x13a8
[ 31.745315] [ T2289] __arm64_sys_finit_module+0x274/0x390
[ 31.745320] [ T2289] invoke_syscall+0x74/0x108
[ 31.745326] [ T2289] el0_svc_common+0x90/0xf8
[ 31.745330] [ T2289] do_el0_svc+0x2c/0x48
[ 31.745333] [ T2289] el0_svc+0x60/0x150
[ 31.745337] [ T2289] el0t_64_sync_handler+0x80/0x118
[ 31.745341] [ T2289] el0t_64_sync+0x1b8/0x1c0
Changes replaces smp_processor_id() with raw_smp_processor_id() to ensure safe CPU ID retrieval in preemptible contexts.
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Analysis
by VulDB Data Team • 01/27/2026
The vulnerability described in CVE-2025-38295 affects the Linux kernel's Amlogic DDR PMU driver, specifically within the meson_ddr_pmu_create() function. This issue stems from an improper use of the smp_processor_id() function, which is designed for use in non-preemptible contexts where preemption is disabled. The function's misuse in a preemptible context leads to kernel warnings and potential instability during module loading, particularly on ARM-based systems such as the Hardkernel ODROID-N2Plus. The error manifests when the udev-worker process attempts to load the driver module, triggering a kernel BUG warning that indicates the function is being called in a context where preemption is enabled, violating kernel safety assumptions.
The technical flaw arises from the incorrect assumption that smp_processor_id() can be safely used in all kernel contexts. This function performs runtime checks to ensure preemption is disabled, and when invoked in preemptible contexts, it generates kernel warnings and can cause system instability. The stack trace clearly shows the call path leading to the issue, with meson_ddr_pmu_create() being the direct source of the problem. The function's invocation occurs during platform driver probe operations, specifically in the g12_ddr_pmu_probe() function, which is part of the standard device driver loading sequence. This improper function usage demonstrates a violation of kernel coding standards and best practices for concurrent execution contexts.
The operational impact of this vulnerability extends beyond simple kernel warnings, as it can lead to system instability during module loading phases. When the Amlogic DDR PMU driver fails to initialize correctly due to this preemption issue, it can affect memory management and performance monitoring capabilities for DDR memory on affected ARM platforms. The vulnerability particularly impacts embedded systems and single-board computers that rely on the Amlogic SoC architecture, potentially causing boot delays or preventing proper memory subsystem initialization. This issue also represents a broader concern for kernel module developers regarding proper handling of CPU identification functions in concurrent contexts, as it demonstrates how seemingly minor coding errors can have significant system-wide implications.
The fix implemented for this vulnerability involves replacing smp_processor_id() with raw_smp_processor_id() within the meson_ddr_pmu_create() function. This change ensures that CPU identification occurs safely in preemptible contexts without triggering kernel warnings. The raw_smp_processor_id() function provides the same basic functionality but without the preemption checks, making it suitable for use in contexts where preemption may be enabled. This solution aligns with established kernel development practices and addresses the specific requirements for the Amlogic DDR PMU driver's operation. The fix directly corresponds to CWE-398, which identifies code that is not maintained, and follows ATT&CK technique T1059.006 for kernel module manipulation, ensuring that system integrity is maintained during driver initialization processes.
The resolution of this vulnerability demonstrates the importance of careful consideration when using kernel synchronization primitives and CPU identification functions across different execution contexts. It underscores the need for kernel developers to understand the implications of preemption and concurrent execution when writing device drivers and system modules. The fix serves as a reminder of the critical nature of proper kernel coding standards and the potential for seemingly minor issues to cause significant system behavior problems. This vulnerability also highlights the importance of thorough testing in preemptible contexts, particularly for device drivers that are loaded during system initialization phases where timing and execution context can be critical for system stability and proper operation.