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CVE-2026-98538

Unknown

Last modified

CVE-2026-98538 is a vulnerability of currently unknown severity. In the Linux kernel, the following vulnerability has been resolved: writeback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes cleanup_offline_cgwb() prepares at most WB_MAX_INODES_PER_ISW inodes per call and is called again until the dying wb is drained, but every call walks wb->b_attached and then wb->b_dirty_time from the same end. Inodes already prepared (they stay on the list with I_WB_SWITCH set until the switch worker runs) and inodes that cannot be switched (I_FREEING, I_WILL_FREE, !SB_ACTIVE, DAX, already on the target wb) stay where they are, so each pass rescans a growing run of them under wb->list_lock and a full drain is quadratic in the number of inodes on the list. With ~17M inodes attached to one dying cgwb we saw this end in soft lockups, with CPUs reported stuck for 21-48s. Walk both lists from the oldest end and move every scanned inode to the newest end, so the next pass starts where the previous one stopped and the drain becomes linear.

Description

In the Linux kernel, the following vulnerability has been resolved: writeback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes cleanup_offline_cgwb() prepares at most WB_MAX_INODES_PER_ISW inodes per call and is called again until the dying wb is drained, but every call walks wb->b_attached and then wb->b_dirty_time from the same end. Inodes already prepared (they stay on the list with I_WB_SWITCH set until the switch worker runs) and inodes that cannot be switched (I_FREEING, I_WILL_FREE, !SB_ACTIVE, DAX, already on the target wb) stay where they are, so each pass rescans a growing run of them under wb->list_lock and a full drain is quadratic in the number of inodes on the list. With ~17M inodes attached to one dying cgwb we saw this end in soft lockups, with CPUs reported stuck for 21-48s. Walk both lists from the oldest end and move every scanned inode to the newest end, so the next pass starts where the previous one stopped and the drain becomes linear. b_attached is unordered, so nobody sees the reorder there. b_dirty_time is ordered by dirtied_when, but the oldest unscanned inode stays at the end move_expired_inodes() picks from, sync takes the whole list regardless of order, and prepared inodes leave the list as soon as the switch work runs and get a new dirtied_time_when on the new wb anyway, so the only inodes left out of order are the ones that can never switch (DAX), and only on the dying wb.

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= c22d70a162d3cc177282c4487be4d54876ca55c8, < 2d1da58c79b66646721a644c6eb4dd1f9c5c9327; >= c22d70a162d3cc177282c4487be4d54876ca55c8, < c96b4d1628868e1195da1a896f79e06f350a3187; >= c22d70a162d3cc177282c4487be4d54876ca55c8, < 624dd0931162523d70f9db8c120b5ec6429a9b97; >= c22d70a162d3cc177282c4487be4d54876ca55c8, < dd4b92067238771b604b59fdda8efed6d70ee823; >= c22d70a162d3cc177282c4487be4d54876ca55c8, < 9dac137bf77e0683778fb34c86e730c6129e8cb6; >= c22d70a162d3cc177282c4487be4d54876ca55c8, < f6988c90671e83db79df1b7b9d6fdb0e5947fd84
LinuxLinux5.14

References

Timeline

Published
Last Modified
Status
Received

Frequently Asked Questions

What is CVE-2026-98538?
In the Linux kernel, the following vulnerability has been resolved: writeback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes cleanup_offline_cgwb() prepares at most WB_MAX_INODES_PER_ISW inodes per call and is called again until the dying wb is drained, but every call walks wb->b_attached and then wb->b_dirty_time from the same end. Inodes already prepared (they stay on the list with I_WB_SWITCH set until the switch worker runs) and inodes that cannot be switched (I_FREEING, I_WILL_FREE, !SB_ACTIVE, DAX, already on the target wb) stay where they are, so each pass rescans a growing run of them under wb->list_lock and a full drain is quadratic in the number of inodes on the list. With ~17M inodes attached to one dying cgwb we saw this end in soft lockups, with CPUs reported stuck for 21-48s. Walk both lists from the oldest end and move every scanned inode to the newest end, so the next pass starts where the previous one stopped and the drain becomes linear. b_attached is unordered, so nobody sees the reorder there. b_dirty_time is ordered by dirtied_when, but the oldest unscanned inode stays at the end move_expired_inodes() picks from, sync takes the whole list regardless of order, and prepared inodes leave the list as soon as the switch work runs and get a new dirtied_time_when on the new wb anyway, so the only inodes left out of order are the ones that can never switch (DAX), and only on the dying wb.
How severe is CVE-2026-98538?
Severity scoring for CVE-2026-98538 is pending analysis.
How do I fix CVE-2026-98538?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST