{ "schema_version": "1.6.1", "id": "RPI-CVE-2024-40900", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2024-40900" ], "published": "2024-07-12T12:21:19Z", "summary": "cachefiles: remove requests from xarray during flushing requests", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncachefiles: remove requests from xarray during flushing requests\n\nEven with CACHEFILES_DEAD set, we can still read the requests, so in the\nfollowing concurrency the request may be used after it has been freed:\n\n mount | daemon_thread1 | daemon_thread2\n------------------------------------------------------------\n cachefiles_ondemand_init_object\n cachefiles_ondemand_send_req\n REQ_A = kzalloc(sizeof(*req) + data_len)\n wait_for_completion(&REQ_A->done)\n cachefiles_daemon_read\n cachefiles_ondemand_daemon_read\n // close dev fd\n cachefiles_flush_reqs\n complete(&REQ_A->done)\n kfree(REQ_A)\n xa_lock(&cache->reqs);\n cachefiles_ondemand_select_req\n req->msg.opcode != CACHEFILES_OP_READ\n // req use-after-free !!!\n xa_unlock(&cache->reqs);\n xa_destroy(&cache->reqs)\n\nHence remove requests from cache->reqs when flushing them to avoid\naccessing freed requests.", "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": [ "1:6.1.21-1+rpt1", "1:6.1.47-1+rpt2", "1:6.1.47-1+rpt4", "1:6.1.54-1+rpt2", "1:6.1.58-1+rpt2", "1:6.1.63-1+rpt1", "1:6.1.73-1+rpt1", "1:6.6.20-1+rpt1", "1:6.6.28-1+rpt1", "1:6.6.31-1+rpt1" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.1.0-rpi1-rpi-v6", "binary_version": "1:6.1.21-1+rpt1" }, { "binary_name": "linux-image-6.1.0-rpi1-rpi-v7", "binary_version": "1:6.1.21-1+rpt1" }, { "binary_name": "linux-image-6.1.0-rpi1-rpi-v7l", "binary_version": "1:6.1.21-1+rpt1" }, { "binary_name": "linux-image-6.1.0-rpi1-rpi-v8", "binary_version": "1:6.1.21-1+rpt1" }, { 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"linux_commit": null, "upstream_version": "6.1.63", "assessment": "upstream version (no usable Linux commit)", "upstream_fixed": "6.1.95" }, "1:6.1.73-1+rpt1": { "linux_commit": null, "upstream_version": "6.1.73", "assessment": "upstream version (no usable Linux commit)", "upstream_fixed": "6.1.95" }, "1:6.6.20-1+rpt1": { "linux_commit": "6f16847710cc0502450788b9f12f0a14d3429668", "upstream_version": "6.6.20", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.6.35" }, "1:6.6.28-1+rpt1": { "linux_commit": "0c341f47adc3578cd5f817aa20ee2b7f9ae6b23e", "upstream_version": "6.6.28", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.6.35" }, "1:6.6.31-1+rpt1": { "linux_commit": "c1432b4bae5b6582f4d32ba381459f33c34d1424", "upstream_version": "6.6.31", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.6.35" } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2024-40900" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/9f13aacdd4ee9a7644b2a3c96d67113cd083c9c7" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/50d0e55356ba5b84ffb51c42704126124257e598" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/37e19cf86a520d65de1de9cb330415c332a40d19" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/0fc75c5940fa634d84e64c93bfc388e1274ed013" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T11:52:36Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.8, "cvss_v3_severity": "High", "scenario": "AV:L - The vulnerability is reached through local file access on an erofs/fscache on-demand mount and `read()` on the `/dev/cachefiles` character device; no network or adjacent-network data path is involved.\nAC:L - The attacker controls all sides of the race \u2014 pending requests are created on demand by repeated reads of uncached ranges, the flush is inducible via cache-backing I/O errors or daemon teardown, and the daemon's `read()` loop is permanently armed by design, so the window can be hit repeatedly with retries costing nothing.\nPR:L - An unprivileged local user on a host using erofs-on-demand (container lazy image loading) supplies the freed request by reading cached files and sprays the freed slab slot; the CAP_SYS_ADMIN daemon is the victim racer running by design, not a capability the attacker needs.\nUI:N - No victim action is required \u2014 the cachefiles daemon is already blocked in `read()` on `/dev/cachefiles` as part of normal operation, and the flush is triggered by the attacker's own activity or routine daemon teardown.\nS:U - The corruption and its consequences are confined to the kernel's own security authority; this is a standard local kernel compromise with no VM, IOMMU, or hypervisor boundary crossed.\nC:H - The freed `cachefiles_req` is re-read and `copy_to_user(_buffer, msg, msg->len)` copies freed-slab contents to userspace with a length taken from the freed object, and the controlled `req->object` pointer chain yields further arbitrary kernel reads.\nI:H - After heap-spraying the freed allocation, `cachefiles_ondemand_set_object_reopening(object)` writes through the attacker-controlled pointer and `queue_work(fscache_wq, &info->ondemand_work)` executes a `work_struct.func` at an attacker-chosen address, giving arbitrary write and control-flow hijack.\nA:H - The slab use-after-free reliably oopses the kernel \u2014 KASAN-confirmed slab-use-after-free with a wild pointer dereference in the daemon read path \u2014 and can be retriggered at will, panicking the system." } } }