CVE-2021-47189 (GCVE-0-2021-47189)
Vulnerability from cvelistv5
Published
2024-04-10 18:56
Modified
2026-08-05 08:46
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix memory ordering between normal and ordered work functions Ordered work functions aren't guaranteed to be handled by the same thread which executed the normal work functions. The only way execution between normal/ordered functions is synchronized is via the WORK_DONE_BIT, unfortunately the used bitops don't guarantee any ordering whatsoever. This manifested as seemingly inexplicable crashes on ARM64, where async_chunk::inode is seen as non-null in async_cow_submit which causes submit_compressed_extents to be called and crash occurs because async_chunk::inode suddenly became NULL. The call trace was similar to: pc : submit_compressed_extents+0x38/0x3d0 lr : async_cow_submit+0x50/0xd0 sp : ffff800015d4bc20 <registers omitted for brevity> Call trace: submit_compressed_extents+0x38/0x3d0 async_cow_submit+0x50/0xd0 run_ordered_work+0xc8/0x280 btrfs_work_helper+0x98/0x250 process_one_work+0x1f0/0x4ac worker_thread+0x188/0x504 kthread+0x110/0x114 ret_from_fork+0x10/0x18 Fix this by adding respective barrier calls which ensure that all accesses preceding setting of WORK_DONE_BIT are strictly ordered before setting the flag. At the same time add a read barrier after reading of WORK_DONE_BIT in run_ordered_work which ensures all subsequent loads would be strictly ordered after reading the bit. This in turn ensures are all accesses before WORK_DONE_BIT are going to be strictly ordered before any access that can occur in ordered_func.
References
Impacted products
Vendor Product Version
Linux Linux Version: 08a9ff3264181986d1d692a4e6fce3669700c9f8
Version: 08a9ff3264181986d1d692a4e6fce3669700c9f8
Version: 08a9ff3264181986d1d692a4e6fce3669700c9f8
Version: 08a9ff3264181986d1d692a4e6fce3669700c9f8
Version: 08a9ff3264181986d1d692a4e6fce3669700c9f8
Version: 08a9ff3264181986d1d692a4e6fce3669700c9f8
Version: 08a9ff3264181986d1d692a4e6fce3669700c9f8
Version: 08a9ff3264181986d1d692a4e6fce3669700c9f8
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The only way execution between\\nnormal/ordered functions is synchronized is via the WORK_DONE_BIT,\\nunfortunately the used bitops don\u0027t 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    \u003cregisters omitted for brevity\u003e\\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.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.4.293\", \"versionStartIncluding\": \"3.15\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.9.291\", \"versionStartIncluding\": \"3.15\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.14.256\", \"versionStartIncluding\": \"3.15\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.19.218\", \"versionStartIncluding\": \"3.15\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.4.162\", \"versionStartIncluding\": \"3.15\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.82\", \"versionStartIncluding\": \"3.15\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.5\", \"versionStartIncluding\": \"3.15\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.16\", \"versionStartIncluding\": \"3.15\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-08-05T08:46:35.936Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-47189\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-05T08:46:35.936Z\", \"dateReserved\": \"2024-03-25T09:12:14.113Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-04-10T18:56:28.194Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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