{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2021-47189", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-03-25T09:12:14.113Z", "datePublished": "2024-04-10T18:56:28.194Z", "dateUpdated": "2026-08-05T08:46:35.936Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T08:46:35.936Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix memory ordering between normal and ordered work functions\n\nOrdered work functions aren't guaranteed to be handled by the same thread\nwhich executed the normal work functions. The only way execution between\nnormal/ordered functions is synchronized is via the WORK_DONE_BIT,\nunfortunately the used bitops don't guarantee any ordering whatsoever.\n\nThis manifested as seemingly inexplicable crashes on ARM64, where\nasync_chunk::inode is seen as non-null in async_cow_submit which causes\nsubmit_compressed_extents to be called and crash occurs because\nasync_chunk::inode suddenly became NULL. The call trace was similar to:\n\n pc : submit_compressed_extents+0x38/0x3d0\n lr : async_cow_submit+0x50/0xd0\n sp : ffff800015d4bc20\n\n \n\n Call trace:\n submit_compressed_extents+0x38/0x3d0\n async_cow_submit+0x50/0xd0\n run_ordered_work+0xc8/0x280\n btrfs_work_helper+0x98/0x250\n process_one_work+0x1f0/0x4ac\n worker_thread+0x188/0x504\n kthread+0x110/0x114\n ret_from_fork+0x10/0x18\n\nFix this by adding respective barrier calls which ensure that all\naccesses preceding setting of WORK_DONE_BIT are strictly ordered before\nsetting the flag. At the same time add a read barrier after reading of\nWORK_DONE_BIT in run_ordered_work which ensures all subsequent loads\nwould be strictly ordered after reading the bit. This in turn ensures\nare all accesses before WORK_DONE_BIT are going to be strictly ordered\nbefore any access that can occur in ordered_func." } ], "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 bug is in btrfs async workqueue ordering during local writeback (write/fsync → delalloc → cow_file_range_async / btrfs_wq_submit_bio), not in a network-facing protocol handler.\nAC:L - An attacker can create many concurrent compression/async bio work items so worker threads race on WORK_DONE_BIT visibility; this manifested under load on ARM64 without relying on conditions outside attacker influence.\nPR:L - An unprivileged user with write access to a mounted btrfs (e.g. home directory) can trigger the path, and can enable per-file compression via chattr/FS_IOC_SETFLAGS on files they own.\nUI:N - The attacker triggers writeback themselves via ordinary writes/fsync; no separate victim action is required.\nS:U - Impact stays within the host kernel privilege boundary; this is not a VM/IOMMU/sandbox escape.\nC:H - Missing barriers allow ordered_func to observe torn producer state (extent lists, page pointer arrays, bio/csum fields), which can yield wild/stale pointer use and arbitrary kernel memory disclosure.\nI:H - The same torn shared state can drive submit paths with inconsistent pointers/metadata (compressed extent submission or async bio mapping), enabling memory corruption and integrity compromise beyond a clean crash.\nA:H - The bug causes kernel NULL dereferences and oops/hangs in async_cow_submit/submit_compressed_extents, as seen on ARM64." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/btrfs/async-thread.c" ], "versions": [ { "version": "08a9ff3264181986d1d692a4e6fce3669700c9f8", "lessThan": "bd660a20fea3ec60a49709ef5360f145ec0fe779", "status": "affected", "versionType": "git" }, { "version": "08a9ff3264181986d1d692a4e6fce3669700c9f8", "lessThan": "637d652d351fd4f263ef302dc52f3971d314e500", "status": "affected", "versionType": "git" }, { "version": "08a9ff3264181986d1d692a4e6fce3669700c9f8", "lessThan": "804a9d239ae9cbe88e861a7cd62319cc6ec7b136", "status": "affected", "versionType": "git" }, { "version": "08a9ff3264181986d1d692a4e6fce3669700c9f8", "lessThan": "ed058d735a70f4b063323f1a7bb33cda0f987513", "status": "affected", "versionType": "git" }, { "version": "08a9ff3264181986d1d692a4e6fce3669700c9f8", "lessThan": "670f6b3867c8f0f11e5097f353b164cecfec6179", "status": "affected", "versionType": "git" }, { "version": "08a9ff3264181986d1d692a4e6fce3669700c9f8", "lessThan": "6adbc07ebcaf8bead08b21687d49e0fc94400987", "status": "affected", "versionType": "git" }, { "version": "08a9ff3264181986d1d692a4e6fce3669700c9f8", "lessThan": "47e6f9f69153247109042010f3a77579e9dc61ff", "status": "affected", "versionType": "git" }, { "version": "08a9ff3264181986d1d692a4e6fce3669700c9f8", "lessThan": "45da9c1767ac31857df572f0a909fbe88fd5a7e9", "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/btrfs/async-thread.c" ], "versions": [ { "version": "3.15", "status": "affected" }, { "version": "0", "lessThan": "3.15", "status": "unaffected", "versionType": "semver" }, { "version": "4.4.293", "lessThanOrEqual": "4.4.*", "status": "unaffected", "versionType": "semver" }, { "version": "4.9.291", "lessThanOrEqual": "4.9.*", "status": "unaffected", "versionType": "semver" }, { "version": "4.14.256", "lessThanOrEqual": "4.14.*", "status": "unaffected", "versionType": "semver" }, { "version": "4.19.218", "lessThanOrEqual": "4.19.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.4.162", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.82", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.5", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.16", "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": "3.15", "versionEndExcluding": "4.4.293" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.15", "versionEndExcluding": "4.9.291" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.15", "versionEndExcluding": "4.14.256" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.15", "versionEndExcluding": "4.19.218" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.15", "versionEndExcluding": "5.4.162" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.15", "versionEndExcluding": "5.10.82" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.15", "versionEndExcluding": "5.15.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.15", "versionEndExcluding": "5.16" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/bd660a20fea3ec60a49709ef5360f145ec0fe779" }, { "url": "https://git.kernel.org/stable/c/637d652d351fd4f263ef302dc52f3971d314e500" }, { "url": 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