{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2024-56547",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2024-12-27T14:03:05.989Z",
        "datePublished": "2024-12-27T14:11:28.548Z",
        "dateUpdated": "2026-05-11T20:54:27.563Z"
    },
    "containers": {
        "cna": {
            "providerMetadata": {
                "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
                "shortName": "Linux",
                "dateUpdated": "2026-05-11T20:54:27.563Z"
            },
            "descriptions": [
                {
                    "lang": "en",
                    "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nrcu/nocb: Fix missed RCU barrier on deoffloading\n\nCurrently, running rcutorture test with torture_type=rcu fwd_progress=8\nn_barrier_cbs=8 nocbs_nthreads=8 nocbs_toggle=100 onoff_interval=60\ntest_boost=2, will trigger the following warning:\n\n\tWARNING: CPU: 19 PID: 100 at kernel/rcu/tree_nocb.h:1061 rcu_nocb_rdp_deoffload+0x292/0x2a0\n\tRIP: 0010:rcu_nocb_rdp_deoffload+0x292/0x2a0\n\t Call Trace:\n\t  <TASK>\n\t  ? __warn+0x7e/0x120\n\t  ? rcu_nocb_rdp_deoffload+0x292/0x2a0\n\t  ? report_bug+0x18e/0x1a0\n\t  ? handle_bug+0x3d/0x70\n\t  ? exc_invalid_op+0x18/0x70\n\t  ? asm_exc_invalid_op+0x1a/0x20\n\t  ? rcu_nocb_rdp_deoffload+0x292/0x2a0\n\t  rcu_nocb_cpu_deoffload+0x70/0xa0\n\t  rcu_nocb_toggle+0x136/0x1c0\n\t  ? __pfx_rcu_nocb_toggle+0x10/0x10\n\t  kthread+0xd1/0x100\n\t  ? __pfx_kthread+0x10/0x10\n\t  ret_from_fork+0x2f/0x50\n\t  ? __pfx_kthread+0x10/0x10\n\t  ret_from_fork_asm+0x1a/0x30\n\t  </TASK>\n\nCPU0                               CPU2                          CPU3\n//rcu_nocb_toggle             //nocb_cb_wait                   //rcutorture\n\n// deoffload CPU1             // process CPU1's rdp\nrcu_barrier()\n    rcu_segcblist_entrain()\n        rcu_segcblist_add_len(1);\n        // len == 2\n        // enqueue barrier\n        // callback to CPU1's\n        // rdp->cblist\n                             rcu_do_batch()\n                                 // invoke CPU1's rdp->cblist\n                                 // callback\n                                 rcu_barrier_callback()\n                                                             rcu_barrier()\n                                                               mutex_lock(&rcu_state.barrier_mutex);\n                                                               // still see len == 2\n                                                               // enqueue barrier callback\n                                                               // to CPU1's rdp->cblist\n                                                               rcu_segcblist_entrain()\n                                                                   rcu_segcblist_add_len(1);\n                                                                   // len == 3\n                                 // decrement len\n                                 rcu_segcblist_add_len(-2);\n                             kthread_parkme()\n\n// CPU1's rdp->cblist len == 1\n// Warn because there is\n// still a pending barrier\n// trigger warning\nWARN_ON_ONCE(rcu_segcblist_n_cbs(&rdp->cblist));\ncpus_read_unlock();\n\n                                                                // wait CPU1 to comes online and\n                                                                // invoke barrier callback on\n                                                                // CPU1 rdp's->cblist\n                                                                wait_for_completion(&rcu_state.barrier_completion);\n// deoffload CPU4\ncpus_read_lock()\n  rcu_barrier()\n    mutex_lock(&rcu_state.barrier_mutex);\n    // block on barrier_mutex\n    // wait rcu_barrier() on\n    // CPU3 to unlock barrier_mutex\n    // but CPU3 unlock barrier_mutex\n    // need to wait CPU1 comes online\n    // when CPU1 going online will block on cpus_write_lock\n\nThe above scenario will not only trigger a WARN_ON_ONCE(), but also\ntrigger a deadlock.\n\nThanks to nocb locking, a second racing rcu_barrier() on an offline CPU\nwill either observe the decremented callback counter down to 0 and spare\nthe callback enqueue, or rcuo will observe the new callback and keep\nrdp->nocb_cb_sleep to false.\n\nTherefore check rdp->nocb_cb_sleep before parking to make sure no\nfurther rcu_barrier() is waiting on the rdp."
                }
            ],
            "affected": [
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "kernel/rcu/tree_nocb.h"
                    ],
                    "versions": [
                        {
                            "version": "1fcb932c8b5ce86219d7dedcd63659351a43291c",
                            "lessThan": "224b62028959858294789772d372dcb36cf5f820",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "1fcb932c8b5ce86219d7dedcd63659351a43291c",
                            "lessThan": "2996980e20b7a54a1869df15b3445374b850b155",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                },
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "kernel/rcu/tree_nocb.h"
                    ],
                    "versions": [
                        {
                            "version": "6.12",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "6.12",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.12.2",
                            "lessThanOrEqual": "6.12.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.13",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }
            ],
            "cpeApplicability": [
                {
                    "nodes": [
                        {
                            "operator": "OR",
                            "negate": false,
                            "cpeMatch": [
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "6.12",
                                    "versionEndExcluding": "6.12.2"
                                },
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "6.12",
                                    "versionEndExcluding": "6.13"
                                }
                            ]
                        }
                    ]
                }
            ],
            "references": [
                {
                    "url": "https://git.kernel.org/stable/c/224b62028959858294789772d372dcb36cf5f820"
                },
                {
                    "url": "https://git.kernel.org/stable/c/2996980e20b7a54a1869df15b3445374b850b155"
                }
            ],
            "title": "rcu/nocb: Fix missed RCU barrier on deoffloading",
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                "engine": "bippy-1.2.0"
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}