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CVE-2025-21693 is a use-after-free flaw in the Linux kernel zswap subsystem's handling of per-CPU asynchronous compression contexts. zswap_compress() and zswap_decompress() obtain the current CPU's acomp_ctx but may subsequently execute after task migration because preemption and migration are not disabled for the sleepable crypto_acomp API path. If the originally selected CPU is offlined during the operation, the CPU-hotplug teardown path can free resources associated with that context, including its compression buffer, request, and asynchronous-compression object, while compression or decompression still uses them. The upstream fix serializes CPU-hotplug allocation and teardown with compression and decompression through the per-CPU acomp_ctx mutex, marks freed contexts by clearing the request pointer, and retries operations when the selected context was offlined.
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Linux kernel zswap resource-free synchronization flaw.
A Linux kernel zswap use-after-free vulnerability caused by insufficient synchronization between compression/decompression operations and CPU hot-unplug resource cleanup for per-CPU crypto_acomp contexts.
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Cross-references every affected SKU, including bundled OEM variants.
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