{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2021-47493", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-05-22T06:20:56.201Z", "datePublished": "2024-05-22T08:19:41.419Z", "dateUpdated": "2026-08-05T08:48:03.801Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T08:48:03.801Z" }, "descriptions": [ { "lang": "en", "value": "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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The vulnerable path is reached via local filesystem operations (write/create → ocfs2_file_write_iter / namei → ocfs2_reserve_clusters → ocfs2_block_group_find_clear_bits → ocfs2_test_bg_bit_allocatable) on a mounted OCFS2 volume, not via network packet processing or physical device attachment.\nAC:L - An unprivileged attacker can drive both sides of the race by running concurrent writers/creators that trigger cluster bitmap searches while forcing journal commits (sync/fsync and heavy metadata activity), so winning the unprotected bh2jh window is attacker-controlled and retryable.\nPR:L - Once OCFS2 is mounted (typical shared-cluster deployment), any unprivileged local user with write permission to files or directories can exercise the allocation path; no CAP_SYS_ADMIN or init-namespace root is required along the vulnerable code path.\nUI:N - The attacker performs the concurrent writes and syncs themselves; no separate victim action such as opening a crafted file or confirming a prompt is required beyond the filesystem already being mounted.\nS:U - Impact is kernel memory corruption / oops within the same host OS authority (OCFS2/JBD2), with no VM escape, IOMMU bypass, or other cross-boundary scope change.\nC:H - Between bh2jh() and use of the journal_head, jbd2 can free the object, creating a use-after-free; per guidance a UAF enables heap reclaim and arbitrary kernel read primitives.\nI:H - The same journal_head UAF (spin_lock and access to b_committed_data on a freed slab object) is exploitable via heap spray for write and control-flow hijacking primitives in the kernel.\nA:H - The observed race already causes a kernel page-fault panic (NULL or dangling journal_head dereference in ocfs2_block_group_find_clear_bits), which is full availability impact even without a complete exploit." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/ocfs2/suballoc.c" ], "versions": [ { "version": "ccd979bdbce9fba8412beb3f1de68a9d0171b12c", "lessThan": "5043fbd294f5909a080ade0f04b70a4da9e122b7", "status": "affected", "versionType": "git" }, { "version": "ccd979bdbce9fba8412beb3f1de68a9d0171b12c", "lessThan": "2e382600e8856ea654677b5134ee66e03ea72bc2", "status": "affected", "versionType": "git" }, { "version": "ccd979bdbce9fba8412beb3f1de68a9d0171b12c", "lessThan": "6f1b228529ae49b0f85ab89bcdb6c365df401558", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/ocfs2/suballoc.c" ], "versions": [ { "version": "2.6.16", "status": "affected" }, { "version": "0", "lessThan": "2.6.16", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.77", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.14.16", "lessThanOrEqual": "5.14.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15", "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": "2.6.16", "versionEndExcluding": "5.10.77" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.16", "versionEndExcluding": "5.14.16" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.16", "versionEndExcluding": "5.15" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/5043fbd294f5909a080ade0f04b70a4da9e122b7" }, { "url": "https://git.kernel.org/stable/c/2e382600e8856ea654677b5134ee66e03ea72bc2" }, { "url": "https://git.kernel.org/stable/c/6f1b228529ae49b0f85ab89bcdb6c365df401558" } ], "title": "ocfs2: fix race between searching chunks and release journal_head from buffer_head", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "timestamp": "2024-06-06T18:35:17.607326Z", "id": "CVE-2021-47493", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "partial" } ], "role": "CISA Coordinator", "version": "2.0.3" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2024-06-06T18:35:30.175Z" } }, { "providerMetadata": { "orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-04T05:39:59.750Z" }, "title": "CVE Program Container", "references": [ { "url": "https://git.kernel.org/stable/c/5043fbd294f5909a080ade0f04b70a4da9e122b7", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/2e382600e8856ea654677b5134ee66e03ea72bc2", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/6f1b228529ae49b0f85ab89bcdb6c365df401558", "tags": [ "x_transferred" ] } ] } ] } }