CVE-2024-46840: btrfs: clean up our handling of refs == 0 in snapshot delete

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-09-27 · updated 2026-06-17

Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: clean up our handling of refs == 0 in snapshot delete In reada we BUG_ON(refs == 0), which could be unkind since we aren't holding a lock on the extent leaf and thus could get a transient incorrect answer. In walk_down_proc we also BUG_ON(refs == 0), which could happen if we have extent tree corruption. Change that to return -EUCLEAN. In do_walk_down() we catch this case and handle it correctly, however we return -EIO, which -EUCLEAN is a more appropriate error code. Finally in walk_up_proc we have the same BUG_ON(refs == 0), so convert that to proper error handling. Also adjust the error message so we can actually do something with the information.

Affected products

Linux kernel: before 4.19.322; from 4.20 before 5.4.284; from 5.5 before 5.10.226; from 5.11 before 5.15.167; from 5.16 before 6.1.110; from 6.2 before 6.6.51 — fixed in 4.19.322, 5.10.226, 5.15.167, 5.4.284, 6.1.110, 6.10.10

How to fix

Upgrade to a fixed version: Linux kernel 4.19.322, 5.10.226, 5.15.167, 5.4.284. Check the vendor advisory for mitigations.

References

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