net/sched: act_api: use RCU with deferred freeing for action lifecycle_CVE-2026-53264

{
    "lastseen": "",
    "description": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_api: use RCU with deferred freeing for action lifecycle\n\nWhen NEWTFILTER and DELFILTER are run concurrently it is possible to create a\nrace with an associated action.\n\nLet's illustrate with CPU0 running NEWTFILTER and CPU1 running DELFILTER:\n\n 0: mutex_lock() <-- holds the idr lock\n 0: rcu_read_lock()\n 0: p = idr_find(idr, index) <-- action p is valid (RCU protects IDR)\n 0: mutex_unlock() <-- releases the idr lock\n 1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held\n 1: idr_remove(idr, index) <-- Action removed from IDR\n 1: mutex_unlock() <-- mutex released allowing us to delete the action\n 1: tcf_action_cleanup(p); kfree(p) <-- Kfrees p immediately, no deferral\n 0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- ouch, UAF p points to freed memory\n\nThis patch fixes the race condition between NEWTFILTER and DELFILTER by\nadding struct rcu_head to tc_action used in the deferral and introducing a\ncall_rcu() in the delete path to defer the final kfree().\n\nNote: this is a revert of commit d7fb60b9cafb (\"net_sched: get rid of tcfa_rcu\")\nbut also modernization/simplification to directly use kfree_rcu().\n\nLet's illustrate the new restored code path:\n\n 0: rcu_read_lock()\n 1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held\n 1: idr_remove(idr, index)\n 1: mutex_unlock()\n 1: call_rcu(&p->tcfa_rcu, tcf_action_rcu_free) <-- defer kfree after grace period\n 0: p = idr_find(idr, index)\n 0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- fails, refcnt already 0\n 1: rcu_read_unlock() <-- release so freeing can run after grace period\n\nAfter CPU1 calls idr_remove(), the object is no longer reachable through the IDR.\nCPU0's subsequent idr_find() will return NULL, and even if it still held a\nstale pointer, the immediate kfree() is now deferred until after the RCU grace\nperiod, so no UAF can occur.",
    "published": "2026-06-25T08:39:51.870Z",
    "modified": "2026-06-28T06:41:06.689Z",
    "type": "cve",
    "title": "net/sched: act_api: use RCU with deferred freeing for action lifecycle",
    "source": "Linux",
    "references": "https://git.kernel.org/stable/c/98b2e40879abf0245be5a5b7af69e0f6ff524ac3\nhttps://git.kernel.org/stable/c/18af5d2ef0c4f65787fd1280c8b23286b9f2a835\nhttps://git.kernel.org/stable/c/1f1b98fea6b9ea30507d0f2fbff6750292d097e2\nhttps://git.kernel.org/stable/c/8b136f18ac4b2ace5aaad3305b3f8a5d8165a009\nhttps://git.kernel.org/stable/c/5dd51e09020c65aa53cf128e5e3517cd53b3c113\nhttps://git.kernel.org/stable/c/b60e9391142e983fab2be53497aa8f71fdd09cd5\nhttps://git.kernel.org/stable/c/91d105d2cbe002f9c7b43a6183adedc37e1da1f7\nhttps://git.kernel.org/stable/c/5057e1aca011e51ef51498c940ef96f3d3e8a305",
    "id": "CVE-2026-53264",
    "bulletinFamily": "",
    "cwe": null,
    "cvelist": null,
    "sourceData": "Linux Linux d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\nLinux Linux d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\nLinux Linux d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\nLinux Linux d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\nLinux Linux d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\nLinux Linux d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\nLinux Linux d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\nLinux Linux d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\nLinux Linux 4.14",
    "sourceHref": "",
    "cvss": {
        "score": 7.8,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
        "version": "3.1"
    },
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        "baseScore": 0,
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    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Linux",
    "version": "d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da",
    "vendor": "Linux",
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}