CVE-2021-47189: btrfs: fix memory ordering between normal and ordered work functions
Vulnerability summary
CVE-2021-47189 is a high (CVSS 7.8) vulnerability in linux. EPSS estimates a 0.67% chance of exploitation in the next 30 days, higher than 52% of scored vulnerabilities.
Not severe (CVSS 7.8, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 11 · Related 11Timeline
- 10-04-2024PublishedVulnerability first disclosed.
- 05-08-2026Last modifiedVulnerability information updated.
Description
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.
CVSS metrics
5 scores · 4 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- NVDNIST7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.67%
Chance of exploitation in the next 30 days
Percentile
52%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.67% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeNo weakness data has been published for this record.
Affected systems
Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu88 products
- linuxAll versions (No fix recorded) | < 4.15.0-167.175 | < 5.4.0-97.110
- linux-allwinner-5.19All versions (No fix recorded)
- linux-awsAll versions (No fix recorded) | < 4.15.0-1119.127 | < 5.4.0-1064.67
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ 08a9ff3264181986d1d692a4e6fce3669700c9f8, < bd660a20fea3ec60a49709ef5360f145ec0fe779 | ≥ 08a9ff3264181986d1d692a4e6fce3669700c9f8, < 637d652d351fd4f263ef302dc52f3971d314e500 | ≥ 08a9ff3264181986d1d692a4e6fce3669700c9f8, < 804a9d239ae9cbe88e861a7cd62319cc6ec7b136 | ≥ 08a9ff3264181986d1d692a4e6fce3669700c9f8, < ed058d735a70f4b063323f1a7bb33cda0f987513 | ≥ 08a9ff3264181986d1d692a4e6fce3669700c9f8, < 670f6b3867c8f0f11e5097f353b164cecfec6179 | ≥ 08a9ff3264181986d1d692a4e6fce3669700c9f8, < 6adbc07ebcaf8bead08b21687d49e0fc94400987 | ≥ 08a9ff3264181986d1d692a4e6fce3669700c9f8, < 47e6f9f69153247109042010f3a77579e9dc61ff | ≥ 08a9ff3264181986d1d692a4e6fce3669700c9f8, < 45da9c1767ac31857df572f0a909fbe88fd5a7e9 | 3.15
- linux_kernel≥ 3.15, < 4.4.293 | ≥ 4.5, < 4.9.291 | ≥ 4.10, < 4.14.256 | ≥ 4.15, < 4.19.218 | ≥ 4.20, < 5.4.162 | ≥ 5.5, < 5.10.82 | ≥ 5.11, < 5.15.5 | 5.16:rc1
Debian1 product
- linux< 5.15.5-1
3 vendors · 91 products
