{"cve":"CVE-2021-47493","nvd":{"published":"2024-05-22T09:15:11.100","modified":"2026-08-04T10:17:05.613","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nocfs2: fix race between searching chunks and release journal_head from buffer_head\n\nEncountered a race between ocfs2_test_bg_bit_allocatable() and\njbd2_journal_put_journal_head() resulting in the below vmcore.\n\n  PID: 106879  TASK: ffff880244ba9c00  CPU: 2   COMMAND: \"loop3\"\n  Call trace:\n    panic\n    oops_end\n    no_context\n    __bad_area_nosemaphore\n    bad_area_nosemaphore\n    __do_page_fault\n    do_page_fault\n    page_fault\n      [exception RIP: ocfs2_block_group_find_clear_bits+316]\n    ocfs2_block_group_find_clear_bits [ocfs2]\n    ocfs2_cluster_group_search [ocfs2]\n    ocfs2_search_chain [ocfs2]\n    ocfs2_claim_suballoc_bits [ocfs2]\n    __ocfs2_claim_clusters [ocfs2]\n    ocfs2_claim_clusters [ocfs2]\n    ocfs2_local_alloc_slide_window [ocfs2]\n    ocfs2_reserve_local_alloc_bits [ocfs2]\n    ocfs2_reserve_clusters_with_limit [ocfs2]\n    ocfs2_reserve_clusters [ocfs2]\n    ocfs2_lock_refcount_allocators [ocfs2]\n    ocfs2_make_clusters_writable [ocfs2]\n    ocfs2_replace_cow [ocfs2]\n    ocfs2_refcount_cow [ocfs2]\n    ocfs2_file_write_iter [ocfs2]\n    lo_rw_aio\n    loop_queue_work\n    kthread_worker_fn\n    kthread\n    ret_from_fork\n\nWhen ocfs2_test_bg_bit_allocatable() called bh2jh(bg_bh), the\nbg_bh->b_private NULL as jbd2_journal_put_journal_head() raced and\nreleased the jounal head from the buffer head.  Needed to take bit lock\nfor the bit 'BH_JournalHead' to fix this race.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H","score":4.7},"cwes":["CWE-362"],"references":["https://git.kernel.org/stable/c/2e382600e8856ea654677b5134ee66e03ea72bc2","https://git.kernel.org/stable/c/5043fbd294f5909a080ade0f04b70a4da9e122b7","https://git.kernel.org/stable/c/6f1b228529ae49b0f85ab89bcdb6c365df401558","https://git.kernel.org/stable/c/2e382600e8856ea654677b5134ee66e03ea72bc2","https://git.kernel.org/stable/c/5043fbd294f5909a080ade0f04b70a4da9e122b7"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:50:30.954589733+00:00"},"epss":{"cve":"CVE-2021-47493","score":0.00173,"percentile":0.06693,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}