Executive brief
A vulnerability in the Linux kernel's Device Mapper (DM) component can cause system performance issues or instability. The issue occurs when certain storage operations are incorrectly slowed down (throttled), potentially leading to a denial-of-service condition where the system becomes unresponsive during heavy disk activity. This affects systems using specific storage configurations like LVM or software RAID.
Technical details
A vulnerability in the Linux kernel's Device Mapper (DM) layer involves unconditional I/O throttling during REQ_PREFLUSH operations. When a bio with REQ_PREFLUSH is submitted, the __send_empty_flush() function generates a flush_bio that is incorrectly throttled by wbt_wait() in the Writeback Throttling (WBT) subsystem. This occurs even when the underlying filesystem (such as XFS) explicitly requests that metadata I/O not be throttled. An attacker with local access could potentially trigger heavy I/O patterns that exploit this behavior to cause a denial-of-service (DoS) by stalling critical kernel worker threads. The fix involves conditionally adding the REQ_IDLE flag to flush_bio.bi_opf to bypass WBT throttling.
Affected products
- Linux Linux Kernel up to 6.1.141, 6.2 to 6.6.93, 6.7 to 6.12.31, 6.13 to 6.14.9
Timeline
- 2025-06-18: disclosed: CVE published and patched in various stable branches.
References
- https://git.kernel.org/stable/c/2858cda9a8d95e6deee7e3b0a26adde696a9a4f5
- https://git.kernel.org/stable/c/52aa28f7b1708d76e315d78b5ed397932a1a97c3
- https://git.kernel.org/stable/c/88f7f56d16f568f19e1a695af34a7f4a6ce537a6
- https://git.kernel.org/stable/c/95d08924335f3b6f4ea0b92ebfe4fe0731c502d9
- https://git.kernel.org/stable/c/b55a97d1bd4083729a60d19beffe85d4c96680de
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
- https://cert-portal.siemens.com/productcert/html/ssa-082556.html