{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-89763", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2026-89763" ], "published": "2026-09-11T19:47:07Z", "summary": "KEYS: trusted: Fix TPM teardown ordering", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nKEYS: trusted: Fix TPM teardown ordering\n\ntrusted_tpm_exit() drops the TPM chip reference and frees the digest\narray before unregistering the trusted key type. key_type_lookup()\nholds key_types_sem for reading until the key operation finishes, while\nunregister_key_type() takes it for writing. It therefore provides the\nsynchronization point that must precede backend teardown.\n\nThe current order permits this interleaving:\n\n CPU 0 CPU 1\n trusted_tpm_exit() key_type_lookup(\"trusted\")\n put_device(&chip->dev) trusted_tpm_seal()\n kfree(digests) pcrlock()\n unregister_key_type() tpm_pcr_extend(..., digests)\n\nCPU 1 can consequently dereference the freed digest array. The chip can\nalso be released before callbacks stop using it.\n\nKASAN reported:\n\n BUG: KASAN: slab-use-after-free in tpm_pcr_extend+0x1f0/0x200\n Read of size 2 at addr ffff88810872d000 by task poc/89\n Call Trace:\n tpm_pcr_extend+0x1f0/0x200\n pcrlock+0x42/0x70 [trusted]\n trusted_tpm_seal+0x1b6/0x570 [trusted]\n trusted_instantiate+0x293/0x340 [trusted]\n __key_instantiate_and_link+0xb2/0x2b0\n __key_create_or_update+0x61e/0xb50\n __do_sys_add_key+0x1b8/0x310\n Allocated by task 88:\n __kmalloc_noprof+0x1a7/0x490\n do_one_initcall+0xa1/0x390\n do_init_module+0x2df/0x840\n Freed by task 90:\n kfree+0x131/0x3c0\n trusted_tpm_exit+0x59/0xa0 [trusted]\n __do_sys_delete_module+0x346/0x510\n\nMove unregister_key_type() before releasing either resource. This stops\nnew lookups and waits for in-flight key operations to finish before the\nbackend state is destroyed.", "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": null, "compiled_filter": false } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-89763" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/3d67b4acbfc7af331d887a8efc04bef6573b8a7a" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/753c978f2400f9783eb524842a975d3ac950d511" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/2f7541afbc57fe9d26769a22c31d8ce8790c9a19" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/5e2d672280d97d83de43031d93761b12dadd7b8a" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-09-21T13:30:03Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.8, "cvss_v3_severity": "High", "scenario": "AV:L - The UAF is reached only via the local add_key(2) syscall (trusted_instantiate \u2192 trusted_tpm_seal \u2192 pcrlock/tpm_* on global chip/digests) racing trusted_tpm_exit() during delete_module of trusted.ko; no network or adjacent protocol processes this key-type teardown.\nAC:L - The attacker controls both sides of the race by issuing concurrent add_key(\"trusted\") while trusted.ko is unloaded; key_type_lookup() still succeeds until unregister_key_type(), so the documented CPU0/CPU1 interleaving is reliably repeatable without uncontrollable victim memory layout.\nPR:L - add_key(2) on a caller-owned keyring has no capable() check in trusted_instantiate(); every seal/unseal uses the global chip after put_device, and only optional pcrlock() needs CAP_SYS_ADMIN. Per CNA driver-removal UAF precedent, concurrent rmmod of trusted.ko does not require the attacker to hold CAP_SYS_MODULE.\nUI:N - Exploitation is driven by the attacker's own add_key threads and module-unload timing; no separate victim must mount a filesystem, open a device, or take any other action.\nS:U - The vulnerability is a standard in-kernel slab use-after-free affecting host kernel memory and availability; it does not cross a VM, IOMMU, or other distinct security-authority boundary.\nC:H - KASAN shows a slab-use-after-free read of the freed digests array in tpm_pcr_extend, and put_device may free tpm_chip while callbacks still dereference it; per kernel CNA guidance a UAF enables object reuse and arbitrary kernel read, so Confidentiality is High.\nI:H - Seal/unseal after teardown calls tpm_try_get_ops() which mutates chip (get_device, mutex_lock) and PCR extend consumes the UAF'd digest buffer; use-after-free is heap-sprayable into write and control-flow primitives, so Integrity is High.\nA:H - The KASAN report is a kernel slab-use-after-free oops during add_key versus delete_module; any such UAF can panic or hang the kernel, scoring Availability High even when not fully exploited for code execution." } } }