CVE-2026-90214 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
ASoC: xilinx: formatter_pcm: fix stream_data leak on open error
In xlnx_formatter_pcm_open(), stream_data is allocated and adata->play_stream or adata->capture_stream is assigned early. If a later step, such as snd_pcm_hw_constraint_step() or snd_pcm_hw_constraint_integer(), fails, the function returns the error immediately. ALSA does not call the close callback when open fails, so stream_data is leaked and the stream pointer is left dangling, pointing to a substream that ALSA frees. A later interrupt would then call snd_pcm_period_elapsed() on the freed substream.
Free stream_data and clear the stream pointer on the error paths.
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Analysis
by VulDB Data Team • 09/17/2026
The vulnerability identified in the Linux kernel's Advanced System-on-Chip sound component for Xilinx hardware, specifically within the formatter PCM driver, represents a critical resource management flaw during device initialization. This issue arises from improper handling of memory allocation and state cleanup when the stream opening process encounters an error condition. The core technical defect lies in the xlnx_formatter_pcm_open function, where dynamic memory is allocated to create a stream_data structure early in the execution flow. Simultaneously, pointers within the audio device context are updated to reference this newly allocated data for either playback or capture streams. This design assumes that if any subsequent initialization step fails, the system will revert these changes and free the associated resources. However, the implementation lacks adequate error handling paths to reverse these assignments before returning an error code to the caller.
The operational impact of this flaw is twofold, involving both memory leakage and potential use-after-free scenarios due to dangling pointers. When a subsequent function call, such as snd_pcm_hw_constraint_step or snd_pcm_hw_constraint_integer, fails, the open routine immediately returns with an error status without invoking cleanup procedures for the previously allocated stream_data structure. Because the ALSA sound subsystem does not trigger the close callback when the open operation itself fails to complete successfully, the allocated memory is never released. This results in a persistent kernel memory leak that can eventually lead to resource exhaustion under repeated failure conditions. More critically, the audio device context retains pointers to the now-invalid stream data because these references were established before the error occurred but are not cleared upon failure.
This state inconsistency creates a severe security risk classified as a use-after-free vulnerability. The dangling pointer in the driver's private data structure continues to reference memory that has been freed by the ALSA subsystem during its own cleanup process following the failed open attempt. If an interrupt occurs while this stale pointer is still active, the kernel may invoke snd_pcm_period_elapsed on the freed substream object. Accessing or modifying a freed memory region can lead to undefined behavior, including system crashes, data corruption, or potentially exploitable conditions where an attacker might influence control flow through heap metadata manipulation. This aligns with CWE-416, which describes use after free errors resulting from improper handling of deallocated resources.
From a threat modeling perspective using the MITRE ATT&CK framework, this vulnerability facilitates exploitation techniques related to privilege escalation or denial of service via memory corruption. An attacker who can trigger repeated open failures on affected audio devices could exhaust kernel memory reserves, causing a denial of service for other system components. Alternatively, if the timing and heap layout allow, an adversary might leverage the use-after-free condition to execute arbitrary code with kernel privileges by overwriting freed memory structures before they are reallocated for different purposes. This highlights the importance of strict resource lifecycle management in kernel-space drivers where direct hardware interaction occurs without user-level safeguards.
To mitigate this vulnerability, developers must ensure that all allocated resources and state changes made during a partially completed initialization sequence are rolled back upon any error condition. Specifically, the xlnx_formatter_pcm_open function requires modification to free the stream_data structure immediately if any subsequent constraint check fails. Furthermore, it is essential to explicitly clear or reset the play_stream and capture_stream pointers in the audio device context to prevent them from pointing to invalid memory addresses. Implementing these cleanup steps ensures that no dangling references remain after a failed open operation, thereby eliminating both the memory leak and the potential for use-after-free exploitation. This approach adheres to secure coding standards that mandate symmetric allocation and deallocation logic within error handling paths.