{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-53161", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2026-53161" ], "published": "2026-06-25T08:41:40Z", "summary": "misc: fastrpc: fix use-after-free of fastrpc_user in workqueue context", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmisc: fastrpc: fix use-after-free of fastrpc_user in workqueue context\n\nThere is a race between fastrpc_device_release() and the workqueue\nthat processes DSP responses. When the user closes the file descriptor,\nfastrpc_device_release() frees the fastrpc_user structure. Concurrently,\nan in-flight DSP invocation can complete and fastrpc_rpmsg_callback()\nschedules context cleanup via schedule_work(&ctx->put_work). If the\nworkqueue runs fastrpc_context_free() in parallel with or after\nfastrpc_device_release() has freed the user structure, it dereferences\nthe freed fastrpc_user. Depending on the state of the context at the\ntime of the race, any one of the following accesses can be hit:\n\n 1. fastrpc_buf_free() calls fastrpc_ipa_to_dma_addr(buf->fl->cctx, ...)\n to strip the SID bits from the stored IOVA before passing the\n physical address to dma_free_coherent().\n\n 2. fastrpc_free_map() reads map->fl->cctx->vmperms[0].vmid to\n reconstruct the source permission bitmask needed for the\n qcom_scm_assign_mem() call that returns memory from the DSP VM\n back to HLOS.\n\n 3. fastrpc_free_map() acquires map->fl->lock to safely remove the\n map node from the fl->maps list.\n\nThe resulting use-after-free manifests as:\n\n pc : fastrpc_buf_free+0x38/0x80 [fastrpc]\n lr : fastrpc_context_free+0xa8/0x1b0 [fastrpc]\n fastrpc_context_free+0xa8/0x1b0 [fastrpc]\n fastrpc_context_put_wq+0x78/0xa0 [fastrpc]\n process_one_work+0x180/0x450\n worker_thread+0x26c/0x388\n\nAdd kref-based reference counting to fastrpc_user. Have each invoke\ncontext take a reference on the user at allocation time and release it\nwhen the context is freed. Release the initial reference in\nfastrpc_device_release() at file close. Move the teardown of the user\nstructure \u2014 freeing pending contexts, maps, mmaps, and the channel\ncontext reference \u2014 into the kref release callback fastrpc_user_free(),\nso that it runs only when the last reference is dropped, regardless of\nwhether that happens at device close or after the final in-flight\ncontext completes.", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.1.47-1+rpt4" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.1.0-rpi3-rpi-2712", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v6", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v8", "binary_version": "1:6.1.47-1+rpt4" } ] }, "database_specific": { "per_version": { "1:6.1.47-1+rpt4": { "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e", "upstream_version": "6.1.47", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.1.176", "compiled_filter": false } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-53161" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/c6e5c2be09f814377d7f1ce97370a5b7b3e02814" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/e1e3a05efe5954d5bad01157d79429d39a67a7ae" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/d42679eef34dd590b694ce3b666c5e2ba10cd4bf" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/df08fadcf0e5f3708365ec3b6d30b5aafd98bea1" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/ecea4967c2bff92c2fafbc59893f711b39f7b152" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/5278ccd357e0d7aeeb1e76c0f3e0e02894a9897c" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/fbe0947420eec18a84638d29468c2d563ce4e6a3" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/e85eb5feca8e254905ffa6c57a3c99c89a674a0f" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T13:16:28Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.8, "cvss_v3_severity": "High", "scenario": "AV:L - The vulnerable code is reached through local FastRPC misc-device file operations and ioctls on /dev/fastrpc-* rather than by network or physical input.\nAC:L - The attacker can create in-flight DSP invokes and race close/interruption against DSP response workqueue cleanup, and the race can be retried under attacker control.\nPR:L - No in-driver capability check gates open or invoke; in plausible Qualcomm/Android deployments an unprivileged local app can reach FastRPC directly or through a HAL-provided fd.\nUI:N - Exploitation requires only attacker-controlled local ioctls, close, and timing; no separate victim action is needed.\nS:U - The memory corruption affects the kernel driver and kernel memory within the same OS security authority, with no VM or sandbox boundary escape inherent to the bug.\nC:H - This is a kernel use-after-free of fastrpc_user reachable from deferred context cleanup, and UAF conditions can be shaped into kernel memory disclosure primitives.\nI:H - The UAF can dereference attacker-reclaimed kernel heap state through buffer/map cleanup paths, making kernel memory corruption and potential control-flow or arbitrary-write exploitation defensible.\nA:H - At minimum the stale fastrpc_user dereference can crash or oops the kernel during workqueue cleanup, causing high availability impact." } } }