CVE-2026-93249 in Linux
Summary
by MITRE • 09/24/2026
In the Linux kernel, the following vulnerability has been resolved:
spi: amlogic-spisg: Make sure clk_init_data is fully initialized
The clk_init_data structure contains several mutually-exclusive members for different methods to specify the possible parents of a clock, prompting drivers to initialize only the members they need. However, not initializing all members may cause subtle issues, which are only exposed when CONFIG_INIT_STACK_ALL_PATTERN or CONFIG_INIT_STACK_NONE is enabled.
aml_spisg_clk_init() fills in init.parent_data, and assumes that init.parent_names is NULL. However, the latter in uninitialized, and thus may cause a crash.
Make sure all members are fully initialized, to fix such bugs, and to avoid future breakage when converting drivers to a different method for specifying the parents.
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Analysis
by VulDB Data Team • 09/24/2026
The Linux kernel's SPI subsystem contains a specific vulnerability within the Amlogic SPISG driver related to improper initialization of data structures used in clock management operations. The core issue resides in the clk_init_data structure, which is designed to hold configuration details for hardware clocks. This structure includes multiple members that are mutually exclusive depending on whether parents for the clock should be specified via an array of pointers or a list of names. While driver developers often optimize by initializing only the specific fields required for their current implementation, this practice introduces significant risk when stack memory is not fully zeroed out during allocation. The vulnerability specifically affects the aml_spisg_clk_init function, which populates the parent_data member to define clock parents using an array of pointers but incorrectly assumes that the parent_names member remains null or irrelevant due to its exclusion from explicit initialization.
This oversight leads to undefined behavior because the uninitialized memory containing stale data in the parent_names field can be misinterpreted by subsequent kernel routines. The severity and visibility of this bug are heavily dependent on compiler configurations, particularly CONFIG_INIT_STACK_ALL_PATTERN and CONFIG_INIT_STACK_NONE. When stack padding is enabled with patterns for debugging or disabled entirely for performance, the residual garbage values left in uninitialized portions of local variables become accessible to the driver logic. Consequently, if the kernel code checks parent_names before verifying that it should be ignored based on the presence of parent_data, it may attempt to dereference invalid pointers or process corrupted strings derived from stack remnants. This scenario can result in a system crash, typically manifesting as a null pointer exception or an out-of-bounds memory access depending on the specific garbage values present at runtime.
From a security and stability perspective, this vulnerability represents a classic case of incomplete initialization leading to unpredictable execution paths. It aligns with CWE-457, which describes the use of an uninitialized variable, as well as CWE-908 regarding the use of uninitialized data in critical logic branches. In terms of attack vectors, while primarily causing denial-of-service through system instability rather than direct privilege escalation, it falls under ATT&CK technique T1496, Resource Hijacking, specifically if the crash leads to resource exhaustion or service unavailability. The flaw highlights a broader architectural weakness where drivers rely on implicit assumptions about memory state that are not guaranteed by the C standard or kernel allocation mechanisms unless explicitly enforced through proper initialization practices.
To mitigate this vulnerability and prevent similar issues in future driver development, it is imperative to ensure that all members of complex structures like clk_init_data are fully initialized before use. This can be achieved by using designated initializers with zeroed defaults for any fields not actively populated or by employing memset operations on the structure prior to assignment. Developers must avoid relying on the assumption that unused fields will remain null, as stack allocation patterns vary across different kernel configurations and compiler versions. Adopting strict initialization protocols ensures consistent behavior regardless of whether CONFIG_INIT_STACK_ALL_PATTERN is enabled, thereby enhancing the robustness of the SPI subsystem against memory corruption errors and maintaining system stability under diverse operational conditions.