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Exploitation unknown; this catalogue does not assess exploitation. ## Source facts (JSON-quoted data) CNA source text (English) id: "CVE-2024-56547" idYear: 2024 status: "PUBLISHED" publishedAt: "2024-12-27T14:11:28.548Z" updatedAt: "2026-05-11T20:54:27.563Z" importedAt: "2026-10-24T01:57:20.494Z" snapshot: {"id":"cve_2026-10-24_midnight_baseline","at":"2026-10-24T00:00:00.000Z","source":"https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z"} url: "https://cveboard.org/cve/CVE-2024-56547" json: "https://cveboard.org/cve/CVE-2024-56547.json" sourceURL: "https://www.cve.org/CVERecord?id=CVE-2024-56547" title: "rcu/nocb: Fix missed RCU barrier on deoffloading" summary: "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 \u003cTASK\u003e\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 \u003c/TASK\u003e\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-\u003ecblist\n rcu_do_batch()\n // invoke CPU1's rdp-\u003ecblist\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-\u003ecblist\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-\u003ecblist len == 1\n// Warn because there is\n// still a pending barrier\n// trigger warning\nWARN_ON_ONCE(rcu_segcblist_n_cbs(&rdp-\u003ecblist));\ncpus_read_unlock();\n\n // wait CPU1 to comes online and\n // invoke barrier callback on\n // CPU1 rdp's-\u003ecblist\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-\u003enocb_cb_sleep to false.\n\nTherefore check rdp-\u003enocb_cb_sleep before parking to make sure no\nfurther rcu_barrier() is waiting on the rdp." affected: [{"versions":[{"version":"1fcb932c8b5ce86219d7dedcd63659351a43291c","status":"affected","versionType":"git","lessThan":"224b62028959858294789772d372dcb36cf5f820"},{"version":"1fcb932c8b5ce86219d7dedcd63659351a43291c","status":"affected","versionType":"git","lessThan":"2996980e20b7a54a1869df15b3445374b850b155"}],"vendor":"Linux","product":"Linux","defaultStatus":"unaffected"},{"versions":[{"version":"6.12","status":"affected"},{"version":"0","status":"unaffected","versionType":"semver","lessThan":"6.12"},{"version":"6.12.2","status":"unaffected","versionType":"semver","lessThanOrEqual":"6.12.*"},{"version":"6.13","status":"unaffected","versionType":"original_commit_for_fix","lessThanOrEqual":"*"}],"vendor":"Linux","product":"Linux","defaultStatus":"affected"}] ## Source licences and attribution CISA Known Exploited Vulnerabilities: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (US government work) GitHub Advisory Database: https://github.com/advisories (CC BY 4.0) Have I Been Pwned: https://haveibeenpwned.com/ (CC BY 4.0) CVE Program (CVE records): https://www.cve.org/Legal/TermsOfUse (CVE Terms of Use) Copyright © 1999-2026, The MITRE Corporation. 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