CVE-2025-38063

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

dm: fix unconditional IO throttle caused by REQ_PREFLUSH

When a bio with REQ_PREFLUSH is submitted to dm, __send_empty_flush()

generates a flush_bio with REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC,

which causes the flush_bio to be throttled by wbt_wait().

An example from v5.4, similar problem also exists in upstream:

crash> bt 2091206

PID: 2091206 TASK: ffff2050df92a300 CPU: 109 COMMAND: "kworker/u260:0"

#0 [ffff800084a2f7f0] __switch_to at ffff80004008aeb8

#1 [ffff800084a2f820] __schedule at ffff800040bfa0c4

#2 [ffff800084a2f880] schedule at ffff800040bfa4b4

#3 [ffff800084a2f8a0] io_schedule at ffff800040bfa9c4

#4 [ffff800084a2f8c0] rq_qos_wait at ffff8000405925bc

#5 [ffff800084a2f940] wbt_wait at ffff8000405bb3a0

#6 [ffff800084a2f9a0] __rq_qos_throttle at ffff800040592254

#7 [ffff800084a2f9c0] blk_mq_make_request at ffff80004057cf38

#8 [ffff800084a2fa60] generic

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References