CVE-2026-53161
Received Received - Intake
Use-After-Free in Linux Kernel FastRPC Subsystem

Publication date: 2026-06-25

Last updated on: 2026-06-25

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: misc: fastrpc: fix use-after-free of fastrpc_user in workqueue context There is a race between fastrpc_device_release() and the workqueue that processes DSP responses. When the user closes the file descriptor, fastrpc_device_release() frees the fastrpc_user structure. Concurrently, an in-flight DSP invocation can complete and fastrpc_rpmsg_callback() schedules context cleanup via schedule_work(&ctx->put_work). If the workqueue runs fastrpc_context_free() in parallel with or after fastrpc_device_release() has freed the user structure, it dereferences the freed fastrpc_user. Depending on the state of the context at the time of the race, any one of the following accesses can be hit: 1. fastrpc_buf_free() calls fastrpc_ipa_to_dma_addr(buf->fl->cctx, ...) to strip the SID bits from the stored IOVA before passing the physical address to dma_free_coherent(). 2. fastrpc_free_map() reads map->fl->cctx->vmperms[0].vmid to reconstruct the source permission bitmask needed for the qcom_scm_assign_mem() call that returns memory from the DSP VM back to HLOS. 3. fastrpc_free_map() acquires map->fl->lock to safely remove the map node from the fl->maps list. The resulting use-after-free manifests as: pc : fastrpc_buf_free+0x38/0x80 [fastrpc] lr : fastrpc_context_free+0xa8/0x1b0 [fastrpc] fastrpc_context_free+0xa8/0x1b0 [fastrpc] fastrpc_context_put_wq+0x78/0xa0 [fastrpc] process_one_work+0x180/0x450 worker_thread+0x26c/0x388 Add kref-based reference counting to fastrpc_user. Have each invoke context take a reference on the user at allocation time and release it when the context is freed. Release the initial reference in fastrpc_device_release() at file close. Move the teardown of the user structure — freeing pending contexts, maps, mmaps, and the channel context reference — into the kref release callback fastrpc_user_free(), so that it runs only when the last reference is dropped, regardless of whether that happens at device close or after the final in-flight context completes.
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Meta Information
Published
2026-06-25
Last Modified
2026-06-25
Generated
2026-06-25
AI Q&A
2026-06-25
EPSS Evaluated
N/A
NVD
CVE-2026-53161
EUVD
EUVD-2026-39252
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
qualcomm fastrpc *
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Exploitability
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CWE ID Description
CWE-UNKNOWN
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Executive Summary

This vulnerability is a use-after-free issue in the Linux kernel's fastrpc component. It occurs due to a race condition between the function that releases the fastrpc user structure when a file descriptor is closed and a workqueue that processes DSP responses. If the workqueue tries to access the fastrpc_user structure after it has been freed, it leads to dereferencing freed memory, which can cause crashes or undefined behavior.

The problem arises because the fastrpc_user structure is freed in fastrpc_device_release() when the user closes the file descriptor, but an in-flight DSP invocation can still complete and schedule cleanup work that accesses this freed structure. The fix involves adding reference counting to ensure the structure is only freed after all references are released.

Impact Analysis

This use-after-free vulnerability can lead to system instability, including crashes or potential execution of arbitrary code if exploited. Since it involves dereferencing freed memory, it may cause kernel panics or other unpredictable behavior, potentially affecting the reliability and security of systems using the affected fastrpc component.

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