# CVE-2021-47189: linux: In the Linux kernel, the following vulnerability has been resolved: btrfs: fix memory ordering between normal and or... CVE-2021-47189 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47189, released April 10, 2024. It is not reported as exploited. Patch Radar priority: High. - Web page: https://patchblox.com/security/cve/CVE-2021-47189 - Priority: High - CVSS: 7.8 (high) - EPSS: 0.0067 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Apr 10, 2024 ## 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 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. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | linux Debian 12.15 (bookworm) | 5.15.5-1 | [DEBIAN-CVE-2021-47189](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47189.md) | Apr 10, 2024 | | Linux | linux Debian 13.5 (trixie) | 5.15.5-1 | [DEBIAN-CVE-2021-47189](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47189.md) | Apr 10, 2024 | | Linux | linux Debian 14 | 5.15.5-1 | [DEBIAN-CVE-2021-47189](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47189.md) | Apr 10, 2024 | --- Data as of 2026-11-08T19:12:23Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.