misc: fastrpc: fix use-after-free of fastrpc_user in workqueue context

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Summary

CVECVE-2026-53161
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-25 09:16:33 UTC
Updated2026-06-25 09:16:33 UTC
DescriptionIn 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 6cffd79504ce040f460831030d3069fa1c99bb71 c6e5c2be09f814377d7f1ce97370a5b7b3e02814 git Not specified
CNA Linux Linux affected 6cffd79504ce040f460831030d3069fa1c99bb71 e1e3a05efe5954d5bad01157d79429d39a67a7ae git Not specified
CNA Linux Linux affected 6cffd79504ce040f460831030d3069fa1c99bb71 d42679eef34dd590b694ce3b666c5e2ba10cd4bf git Not specified
CNA Linux Linux affected 6cffd79504ce040f460831030d3069fa1c99bb71 df08fadcf0e5f3708365ec3b6d30b5aafd98bea1 git Not specified
CNA Linux Linux affected 6cffd79504ce040f460831030d3069fa1c99bb71 ecea4967c2bff92c2fafbc59893f711b39f7b152 git Not specified
CNA Linux Linux affected 6cffd79504ce040f460831030d3069fa1c99bb71 5278ccd357e0d7aeeb1e76c0f3e0e02894a9897c git Not specified
CNA Linux Linux affected 6cffd79504ce040f460831030d3069fa1c99bb71 fbe0947420eec18a84638d29468c2d563ce4e6a3 git Not specified
CNA Linux Linux affected 6cffd79504ce040f460831030d3069fa1c99bb71 e85eb5feca8e254905ffa6c57a3c99c89a674a0f git Not specified
CNA Linux Linux affected 5.1 Not specified
CNA Linux Linux unaffected 5.1 semver Not specified
CNA Linux Linux unaffected 5.10.259 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.210 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.176 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.143 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.94 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.36 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.13 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/5278ccd357e0d7aeeb1e76c0f3e0e02894a9897c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/df08fadcf0e5f3708365ec3b6d30b5aafd98bea1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e1e3a05efe5954d5bad01157d79429d39a67a7ae 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/fbe0947420eec18a84638d29468c2d563ce4e6a3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c6e5c2be09f814377d7f1ce97370a5b7b3e02814 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d42679eef34dd590b694ce3b666c5e2ba10cd4bf 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e85eb5feca8e254905ffa6c57a3c99c89a674a0f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ecea4967c2bff92c2fafbc59893f711b39f7b152 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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